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FAQs on Otocinclus Systems

Related Articles: OtocinclusLoricariids

Related Catfish FAQs: Otocinclus 1, Otocinclus 2, & FAQs on: Otocinclus Identification, Otocinclus Behavior, Otocinclus Compatibility, Otocinclus Selection, Otocinclus Feeding, Otocinclus Health, Otocinclus Reproduction,
Other Loricariid Genera: FAQs on: Ancistrus, Baryancistrus, Genera Farlowella, Loricaria, Sturisoma, Rhineloricaria: Twig Plecostomus, Genera Glyptoperichthys, Liposarcus, Pterygoplichthys, Sailfin Giants among the Loricariids, The Zebra Pleco, Hypancistrus zebra, Hypostomus, Peckoltia: Clown Plecostomus, Lasiancistrus, Pseudacanthicus, Scobanancistrus, L-number catfish,
Suckermouth Catfishes of South and Central America, Loricariid Identification, Loricariid Behavior, Loricariid Compatibility, Loricariid Selection, Loricariid Systems, Loricariid Feeding, Loricariid Reproduction, Loricariid Disease, Catfish: Identification, Behavior, Compatibility, Selection, Systems, Feeding, Disease, Reproduction Algae Eaters

Soft/er, acidic water... highly oxygenated; well-circulated... well-established systems... with green algae (not filamentous) present

Flow rate for a stream manifold Otocinclus vittatus tank
Hi folks,
Thanks for putting together a very informative site.
<A pleasure>
I'm interested in trying to breed the Otocinclus vittatus species, and was wondering what you might suggest as a flow rate for a stream manifold type tank (linear flow).
<Mmm; depending on the arrangement of the motive force... several turn overs per hour>
I've been attempting to research the rivers these naturally occur in, but can't really get a feel for the flow rates. I'm all for the guess and test method as an option, but thought you may have some material on hand.
<Have been to where some members of the genus are collected... flow rates are seasonally high/brisk to quite calm>
I've been keeping about 15 in a school in a 20 gallon with a small school of cardinal tetras, and noticed that the Otos are most active around the output for an Aquaclear 50 or after water changes.
As such, I'm thinking they might appreciate a bit of current or higher dissolved O2.
<Ah yes; concur>
As such, I was thinking of installing a manifold into a new tank similar to what folks use to keep Hillstream loaches, though at considerably lower flow rates.
Current tank is a Walstad-type setup, extremely heavily planted with a gravel/sand cap over soil. Would transition them to a new tank after establishing it for a while.
<I do consider that this is a good idea... again, ten or more turns/h...>
<Thank you for sharing. Bob Fenner>
Re: Flow rate for a stream manifold Otocinclus vittatus tank       7/14/15

<Thank you for sharing. Bob Fenner>
Much obliged! That will be very helpful. I'll start out around 10 turnovers an hour and go from there.
Thanks again!
<A delight; and please do keep us abreast of your observations, experiences here. BobF>

Happy to, thanks!

Otocinclus.. sys., comp., beh.    3/22/11
My name is Jessica, thank you for your help in advance. I have been keeping Goldfish ever since I got my first ten gallon aquarium at the age of nine.
For the past two years, I have had a 29 gallon freshwater planted tank, which is also home to one brand new, week old, two inch Fantail Goldfish and two Otocinclus.
<Mmm... not really compatible fishes... like very different water quality mixes>
The tank parameters are as follows, pH 6.4,
<Low for Goldfish>
Nitrites 0, Nitrates 20ppm or less,
<I would not let the NO3 concentration get any higher than this maximum>
Ammonia 0, and temp 70-72F. I do a weekly 25-50% water change and vacuum the gravel at the same time while tending the plants. It is well water so I don't need to add a dechlorinator. I bought the two Otocinclus about two months ago and they have done an amazing job cleaning up the algae in the tank. At the time the aquarium was home to an eight inch, five year old Bubble Eye Goldfish who has since passed on. His one eye bubble got so big that he kept catching it in his mouth. It became irritated and in the 24 hours that I was not there it managed to become infected and swollen. I placed him in the hospital tank and gave him antibiotics but sadly his eye popped and he died two days later. Since then I have been substituting the Otocinclus's algae diet with some zucchini and spirulina wafers and have left the back and sides of the tank alone for them to clean. When I first got them they both had Ich and one of them had almost its entire caudal fin missing. Unfortunately, I read that this was rather commonplace during the shipping process.
<This is so>
Anyway, its fin has regrown and they both seem to be doing fine. What concerns me is that their dorsal fins always seems to be held tight against their bodies, they have been this way since I got them, is this just normal behavior for them?
<Mmm, yes. A general statement re freshwater fishes is that their fins are "down" for most of the time, vs. marine fishes, whose fins are "up" most of the time>
They seem happy otherwise zooming around the tank and they really love their zucchini, although the new goldfish is fighting them for it. Also, I was thinking of raising the pH just a little bit, up to 6.8, and to this end was thinking of boiling some shells, cracking them, and placing them in a glass bottle in the tank.
<Worth trying>
That way the fish could not get cut on them and they would be easy to take out if the pH got too high. Do you think this is a good idea or would you recommend to just leave the pH alone as is?
<I might instead add a bit of sodium bicarbonate (baking soda) to a given batch of make-up water (in storage and tested ahead of use) to get a proportion of how much you'd be adding to raise the pH on a regular basis... but the shells are again a good/safe source. Bob Fenner>

Oto question, sys., comp., repro.   9/6/2010
Here's a little background.
My wife and I recently setup a new 10 gallon tank.
<A small tank; not recommended for community tanks.
We got an internal filter. We use a heater (which raises the temp by 4 degrees), the temp is usually 73*F without the heater, but based on the fish we had, I thought 77*F would be a better temperature,
<Does depend on the fish.>
and our heater doesn't have a setting (other than on or off). For now we leave it plugged in and achieve 77*F. We started with 2 Neon Tetras, 3 Black Mollies, and 1 Otocinclus.
<72-75 is ideal for Neons and Otocinclus, but tank-bred, fancy Mollies really need slightly warmer conditions, 77-82 F.>
One of the Neons died within 24 hours. The other neon became so lonely, it stopped playing in the bubbles, it stopped eating, and died of loneliness within a week (even the mollies wouldn't play with it when it tried).
<Let's step away from ideas of "playing" and "loneliness". Neon Tetras are difficult to keep unless you have cool, soft water. You're aiming for pH 6-7.5, 3-10 degrees dH. They won't do well in the hard water Mollies MUST have to stay alive. So these two species are NOT compatible. Neons also need to be kept in groups of 6 or more.>
We added 2 more Black Mollies, all these fish so far have come from PetSmart.
<Mollies really won't do well in 10 gallons of water. The males are aggressive towards each other and the females. They are also very sensitive to poor water quality, making them bad choices for new tanks. Do read here:
After a few more visits to PetSmart, we noticed that some of their fish had Ick. We then noticed ours did too. We tried 2 treatments (1 and then another 24 hours later as per the directions) of a bubbling type tablet that was supposed to clear the Ick.
<Hmm'¦ with Mollies, your best bet is the salt/heat method.>
It removed smaller spots of the Ick, but the Mollies still had large amounts on them. Unfortunately we couldn't afford the treatment when we first noticed it.
<Salt is cheap, so not treating fish for Ick shouldn't ever be an issue. While aquarium salt is ideal, any non-iodized salt should work fine as well.>
I think we noticed it on a Tuesday, and we bought the treatment on Saturday and started administering it Saturday evening. One of the female Black Mollies died the Friday before we got the treatment on Saturday. So, by Saturday, we had 2 males and 2 females (Black Mollies). We still had our 1 Oto (I believe female based on the fact it immediately started going up and down the tank and across the tank almost immediately after we got the heater to raise the temp to 77*F.
<You can't sex Otocinclus this way.>
Websites also suggest this is the perfect temp for breeding Otos. (I had no idea).
<Actually, Otocinclus should be kept fairly cool. They are extremely sensitive to low oxygen concentrations, and as you hopefully remember from school, the warmer water gets, the less oxygen it holds.>
As a side note, we also have lots of snails, and they have been fruitful and multiplied. We started with 1 Black Mystery Snail (fully grown) and about 12 baby snails (golden and black mystery mostly). Long story, but we were wanting 2 or 3 babies, but we ended up with about a dozen of them. Most of the baby snails died off (presumably suffocated).
<Actually, Apple/Mystery snails do bad in aquaria. Don't keep them with fish.>
Before we knew it, there were little specs above the water line. Our 2 airstones were moving water rather violently at the surface, and the filter sucks in water, then pours it onto the surface. This was perfect for the snails as they could put their eggs above the waterline and they would constantly be wet by the popping bubbles. I suspect the Otos also enjoyed the constant streams of current as well. By the way, I am sinking every snail egg I find right now. Well, most aquarists would have suggested that a new tank is the least likely scenario for fish to breed. Not only did the snails breed, but the Black Mollies bred.
<As is their wont.>
One day I found a little fry at the bottom. I about had a heart attack since I never even knew the Mollies were thinking of reproducing.
<I think "thinking" is over-egging the pudding a bit. Males will inseminate anything vaguely Molly-like, and do so persistently. In a 10 gallon tank, the females get stressed and often miscarry, which you can recognise because miscarried babies are either stillborn or so weak they fall to the bottom of the tank. Healthy newborn Mollies can swim immediately after they are born, and instinctively hide among floating plants *at the top* of the tank.>
I went to bed and prayed that it would survive.
<Prayer has it's place, I'm sure, but there are some more immediate things you can do to keep Molly fry alive. Do read the above article.>
By the next morning I wanted to save our little Molly and make it some makeshift tank to keep it from being eaten. (Where there's a redneck, there's a way). Keep in mind, that we are very financially struck at this point.
<That's fine. Here's a tip: stick in some floating plants. Floating Indian Fern is ideal, but even "goldfish weed" like Brazilian Pondweed works well. The fry will hide there and won't be eaten. Plus, floating plants give the female cover, and that reduces the stress they get from amorous males.>
So, I found a casing that is used as a top to CD's. (if you go into Wal-mart and state that you want to buy about 50 blank cd's You will get a container that has a very large round lid. Since we still had one of these containers, we simply took the lid off and turned it upside down. It may not be large, but hey, it's what we can afford for the little fry.
<Have done something similar myself. Use a screwdriver to punch a few dozen small holes in the side so water can in and out, and so much the better! If you don't do that, you'll need to change the water in the container at least once a day.>
I went to find it and it was gone. I even moved the shell and gravel around where it had been hiding the night before. We have about 12 large shells throughout the tank.
<Often what happens with very weak fry is they die, snails come into the floating trap overnight, eat the carcass, and then the snails crawl away.>
The gravel is a bit rough and not exactly ideal for fish tanks. I feared it had been eaten. Several days later, we found one that looked similar to it, hiding in the back. I believe it's the same one, my wife disagrees.
<Molly broods can be anything up to 100 fry, though commonly 20-30.>
Either way, we caught it and put it in this makeshift tank I mentioned. My wife got the idea that we should take one of the air stones out and simply place it in the makeshift tank.
This seemed like a good idea at the time. I mentioned that it wont have a filter or heater, but she doesn't have any idea how to solve that. We put a shell in it too. The little fry loves to hide inside the shell, or near the air stone. After trying to look through my daughters binoculars backwards, I did see it fan its underside fin out showing me that it is a female, because the males have a longer pointy fin in that location.
<You can't sex Mollies at this age. The males won't develop their gonopodium until they're about 2 months old. Until then, they look just like females.>
It is still too young to know for sure, but I believe it is a girl. So, now back to the Otos, which is what I am really interested in. Since the one Oto was trying to attract a mate, and there wasn't one, we bought 2 more Otos.
<Not trying to attract a mate, trust me. These are SCHOOLING fish and want companions.>
PetSmart didn't have any and hasn't in the few weeks since we had bought the first one (the only one they had at the time). We had to go all the way to Norman Oklahoma from Bethany Oklahoma just to get Otos that day.
<I assume that's a long way'¦?>
None of the PetSmart stores has any in the greater Oklahoma City area. So we went to "Wet Pets by Steve" in Norman, Oklahoma. We bought 2 Otos (I wanted at least 1 male). When we looked at the Otos, I was unsure how to tell the sexual differences in Otos (I just had some very generic ideas from what I had read online).
<You can't sex them. Mature females become fatter when filled with eggs, but that assumes they're sexually mature and "conditioned". Specimens in pet stores won't have eaten properly for weeks, so the chances of the females being ripe with eggs are next to zero.>
The gist of the online info was that males are smaller and thinner. The females are larger and potentially rounder. I noticed 1 Oto that was certainly different that the one we had. If you could imagine a line between the Otos eyes, and draw a triangle to its tail, that is what our original Oto looked like. But this one was different, the triangle only went down about half way down its body, then narrowed severely. It was almost like it got pinched on the hind end. I figured this meant it was a male, and the ones I am calling triangular are female. The little guy was very active. We bought it, and another one that I believed was female. I figured that if I bought 2 different ones, there would definitely be at least 1 male and female in the tank.
<Actually, you need to get at least six of them for Otocinclus to be happy. Forget about males and females. You can't sex them.>
When we acclimated them to the tank, I noticed that they were a lighter color, they were smaller, and my wife noticed that our original Oto has bigger eyes.
<More than one species in the trade: Otocinclus affinis and Otocinclus vittatus are the commonest.>
The three of them do hang out quite often, but the one I believe is male, is favoring the new female (not the original). None of them are doing the chase and follow routine. I read online that Chinese Algae Eaters are sometimes mistaken for Otos.
<You'd have to be legally blind to confuse Chinese Algae Eaters with Otocinclus! They are completely different. Otocinclus are much smaller, 1.5-2 inches, tops, Otocinclus affinis is grey above with a thick black region along the midline of its body from nose to tail, and off-white below. Otocinclus vittatus is essentially grey above, darker grey along the flanks, with a thin pale band between these two grey regions, and then off-white below. The Chinese Algae Eater (Gyrinocheilus aymonieri) is more or less green all over with a few bluey-green patches along the top surface and a distinctive zig-zag bluey-green stripe along the midline. The Chinese Algae Eater is big, fast-growing fish that gets to about 8 inches within the first year and around 12 inches within the second. It is notoriously aggressive and has no place in a community tank.>
I am hoping that we have 3 Otos. The littlest one (the one I believe is male) is not afraid of the Black Mollies (as the others will get out of the Black Mollies way when picked on). In fact, it even seemed to attack the Black Molly who bothers it. This seemed very strange to me for a tiny fish to stand up to and even fight back against a much larger fish. The Black Mollies have learned to leave it alone.
<Hungry Otocinclus have a bad habit of rasping at the bodies of other fish. They scrape at the body eating the mucous, but in the process they create nasty wounds. Some fish learn to avoid them, which could easily explain why the Molly seems nervous around them.>
The 2 new Otos are about an inch long (or slightly less). I believe our original Oto is full grown, but still short of 2 inches (I have no easy way to estimate its size). So, now on to the good stuff. Long before we added the new Otos, I had performed a 50% water change. In the process, we noticed a clear gel on the back of the filter. Not knowing what it was, we tossed it out. I later, realized it might be Oto eggs. The snails are all mystery snails and lay their eggs above the water line. The Black Mollies are live bearers. The Neon Tetras died before even the idea of multiplying. So by process of elimination, I figured the gel had to be Oto eggs.
<Likely snail eggs.>
A quick reference on the internet confirmed this is a very likely scenario. I eventually noticed 3 new areas of these egg gels. 1 of the gels got scraped while trying to catch the Molly fry. I eventually scraped the rest of it off the side of the tank where it was and let it fall to the bottom. It seems I am finding several of these egg gels now. I am concerned that our tiny male may not even be an adult yet (and that our 2 females may have to continue to be "ladies in waiting"). I noticed one of the group gels just disappear.
<They're snail eggs, likely from Physa or Physella spp. snails. Even if you haven't seen them, they're in there. Fish eggs do not look like clumps of jelly.>
It was truly strange, when my daughters came to visit, I clearly pointed the new gel out and about 2 hours later, the gel was gone. I suspect a molly ate it. That is one of my questions (Will Black Mollies eat Oto eggs?). Next, some of them look ripped, as if something cut them in half. Does this rip mean they hatched ?
<Sure, the snails hatch out within a few days.>
Could a snail have accidentally ripped it when it went over this gel ? The snails are about the same size, or maybe slightly larger. I have kept a pretty detailed "fish log" and it's kind of like a diary of my observations in the tank. Apparently we started the tank 08/07/10 and added fish on 08/08/10. One phrase I used in my fish log (after discovering the Black Mollies like algae tablets and algae on the side of the tank and decorations) is "An Army of Algae Eaters". Yep, every single fish in the tank loves algae. Could be a reason why they thrive when using the 60 watt bulb until it burned out and changed to a 100 watt bulb.
<You're using incandescent bulbs? I would not recommend this. For a start, they're useless for growing plants, and they also waste a lot of electricity. But they're also dangerous -- splashing water on hot bulbs = explosion! If your hood has sockets for incandescent bulbs, I'd STRONGLY suggest replacing the bulb with a much cooler and less wasteful compact fluorescent "bulb".>
I was uneasy with the idea of causing that much algae. We still could see green areas forming on the glass, but our army usually did a pretty well job of cleaning it but couldn't clean it fast enough. We now have a 15 watt bulb. I am concerned how much algae I need to supplement.
<Otocinclus starve quite easily; if they look "hollow bellied", i.e., their bellies are concave, they're starving. Algae wafers are good, but so is blanched lettuce, squished cooked peas, sliced cucumber, sliced zucchini and cooked spinach.>
I dropped algae tablets in the tank and our original Oto never had any thing to do with them. Our Black Mollies loved them. Once we added the 2 new Otos, I tried it again and they (the 2 new Otos) love the algae tablets. So my biggest questions are concerning the Oto eggs. How do we know if they were fertilized ?
<Snail sex is complicated. They're usually hermaphrodites. Some species also have all sorts of fun stuff with 'love darts' well worth reading about.>
How can we know if they are hatched (or damaged). Are the Oto fry good enough at hiding for us to remove them before they get eaten ? And for the strangest question of all.... would it be a bad idea to move some of the Oto eggs to the tank the Black Molly fry is in ? Would she eat the eggs ? Would she eat the fry ? She is still very small (I'm guessing about 1 centimeter long). And finally How many Oto fry hatch from an egg gel ? The gels themselves vary in size as it is. My wife suggested that the gels might be mold. But they are clear.
<They're snail eggs!>
They look like they have white bubble specs in them. If we should try to setup a third makeshift tank, how important is it going to be to have a heater, filter, or airstone ? I'm sure they are Oto eggs because as a test I ran room temperature water over our largest ornament (a ceramic angel where the Otos love to hang out), and shortly later there was an egg gel near the angel. The pictures I could find online of Oto eggs are of 1 to 4 eggs and not a gel. I searched your site, and nothing quite seems to cover these scenarios. But then again, I may be a redneck, and things are always a bit different with rednecks.
<Are they? Forgive this ignorant Englishman not really having a clue what you're talking about.>
So, to make things clear, we now have 4 Black Molly adults (2 female and 2 male), 3 Otos (I believe 2 females and 1 male), and several small snails (the largest one died). In retrospect, maybe the little Oto was protecting eggs I hadn't even noticed yet ? I sure hope it's not a Chinese Algae Eater. I appreciate any and all help you can give me, thanks.
<I hope this helps. Cheers, Neale.>

Otocinclus, L134 Peckoltia; compatibility, systems   3/25/10
Hello there,
I recently returned from a 2 week stint working out of town to find my 5.5 gallon over run with the soft green algae that Otocinclus fish are supposedly fond of. The tank was intended for another project which didn't pan out (my Australe Killifish pair was living happily in my 29 gallon awaiting transfer but couldn't compete for food in my absence and died after the first week.) I had been contemplating adding four Otos to my already cycled 29 gallon and now I'm wondering if the 5.5 would make a suitable quarantine tank or if it is too small even for the short
quarantine period.
<5.5 gallons is really not much good for anything except for a Betta and/or small shrimps, and as you've observed, they are intrinsically unstable and can easily flip into problem mode. You might use it to quarantine very small fish, up to 2.5 cm/1 inch, but other than that, I'd not risk stressing community fish species in such a small tank.>
I removed the majority of the algae with a toothbrush but there is still a fair amount in the tank.
<Algae removal will reduce the problem, but you do have to research why it happened at all.
Without fail, algae comes back if conditions allow.>
There are a couple small plants (Cryptocoryne and some Alternanthera reineckii clippings just floating) and some natural wood decor which have been in the tank for 3 or 4 weeks. The tank itself has been set up for just over a month, I used water from my 29 originally which I dose with aquarium salt as a tonic about every second water change or so.
<Why use salt? The use of "tonic salt" is old school and provides no real benefits.
Is this a reasonable place to keep four Otos for a couple weeks, considering the small size and minor presence of salt?
<Possibly. But Otocinclus require somewhat cool, oxygen rich water with lots of water current. Their mortality in "Nano" tanks is depressingly high, despite their wide sale for such.>
I also wanted to ask whether my leopard frog Pleco which lives in my 29 is indeed a suitable tank mate for Otos or if I have been mislead.
<In a big enough tank with cool (24 C), fast-flowing water and ample green algae, a school of 6 or more Otocinclus affinis/vittatus should coexist with your L134 Peckoltia sp. catfish. Peckoltia spp. feed mostly on the bottom and consume bloodworms and soft vegetables, while Otocinclus graze almost exclusively on green algae from plant leaves. So there shouldn't be much overlap. But L134 prefers warmer water than Otocinclus, so they aren't an obvious or ideal combination. Almost all problems with Otocinclus come down to keeping them too warm, without enough oxygen, or without enough green algae. I doubt 50% of the specimens sold last even 6 months.>
Your time and advice is greatly appreciated.
<Cheers, Neale.>

Should I move my Oto Cats? Sys. mostly   11/15/09
Hi there, sure hope you can give me some advice.
<Will certainly try.>
Three days ago I added 3 oto cats to my 10 gallon aquarium, that they share with a powder blue dwarf Gourami.
<Hmm... not wild about either of these species for casual aquarists (forgive me for saying this if you're a serious aquarist who knows all about them). Colisa lalia is notoriously prone to bacterial and viral diseases, and an awful lot of them die quite soon after purchase. If you've had this specimen a few months, then you may be fine. But do research both Mycobacteria infections and something called Dwarf Gourami Iridovirus.
Neither is curable, both are fatal, and in the case of DGIV, fully 28% of the Colisa lalia exported from Singapore appear to be infected!>
Ammonia - 0
Nitrites - 0
Nitrates - 8
Artificial plants, not much algae
I allowed myself to be convinced by someone at the fish store that they would be great companions to the Gourami, which may be true, however I should have done the research first (doh!) because in hindsight, there is not much algae in that tank, and there are artificial plants, not real.
<Well, plastic plants are not a problem here. They will soon become covered with algae, and to a degree, the Otocinclus will eat this algae. However, and this is a big "however", the types of algae Otocinclus eat are limited to green algae and diatoms. They will not eat blue-green algae, hair algae, thread algae or red algae. Green algae in particular only grows in tanks with good water quality and bright light. Such conditions are usually found in planted aquaria. In tanks where the fishkeeper hasn't bothered with bright lights and is using plastic plants, Otocinclus can starve to death.
I should point out that plastic plants and poor lighting isn't a bad thing in itself, and indeed fish prefer poor lighting and usually show their best colours in shady tanks. But in the case of Otocinclus, it's not what you want.>
They don't appear to be eating algae wafers and I'm worried they will not survive in that tank because of these factors.
<Do also review water temperature (which should be no more than 25 C) and water current (which needs to be brisk, ideally with extra aeration). In short, not the same conditions as Dwarf Gouramis want. Dwarf Gouramis like warm water, around 28-30 C, with a gentle water current.>
I also have a 20 gallon aquarium, that includes 3 oto cats, 1 Farlowella, 7 Corys, 2 swords, and 8 black phantom tetras.
<Ah, now this is a tank that should be maintained quite cool, around 24-25 C, given the mix of fish you have. All these fish like a strong current as well. So this seems like an ideal place for Otocinclus spp., particularly if brightly illuminated.>
Ammonia - 0
Nitrites - 0
Nitrates - 10
25% water change and vacuum weekly
Live plants, 2 large pieces driftwood, some visible algae
<Sounds a nice tank.>
Do you think I should move the 3 Otos that I put in the 10 gallon into the large tank with real plants and more algae?
I'm worried that (1) My Farlowella will lose significant food supply if there are 6 Otos present;
<A risk, but Farlowella should take algae wafers readily enough. You can also supplement with sliced courgette and cucumber, and perhaps strips of Sushi Nori (a good, cheap food for algae eaters generally, and easily bought in Asian food stores).>
and (2) My 20 gallon will be overstocked (which you may tell me is already overstocked without adding 3 more Otos!).
<Three Otocinclus will be neither here nor there. If nitrates are this low, I'd actually be quite comfortable about adding the Otocinclus.>
What do you think?
<Go for it. Certainly more chance of success with them in the 20 gallon than the 10 gallon.>
Thanks so much!
<Cheers, Neale.>

Can and/or do Oto Catfish tolerate slightly brackish water?   5/17/09
I put about a tablespoon of aquarium salt per 5 gallons.
<Why? Adding salt at this concentration does precisely nothing to make your fish healthier or happier. Utter waste of money, and potentially harmful to freshwater fish in the long term.>
If not, what small algae eating fish does well in brackish conditions?
<Best bets are Mollies and other Poeciliidae; algae-eating snails such as Nerites; and salt-tolerant algae-eating shrimps such as Amano shrimps. Most of the large herbivores like Scats will also eat substantial amounts of
algae, though they're not normally used for algae control. As ever, if you have an algae problem, the solution isn't fish but making sure the tank is "balanced", in particular, that there are enough fast-growing plants under strong light. Most algae problems occur in unbalanced aquaria.>
<Cheers, Neale.>

Re: Oto Catfish and brackish water? 5/17/09
Hmm that's weird because I thought that Mollies do best with a little bit of salt...
<They do. One tablespoon per 5 gallons doesn't make brackish water, and neither does it do anything useful for freshwater fish. Adding such a trivially small amount of salt is pointless. Mollies do well upwards of 6 grammes per litre, which is about one level teaspoon per litre, and one litre is 3.75 US gallons, so that's about 3.75 teaspoons per US gallon. Since one tablespoon is three teaspoons, that's a bit over a tablespoon per gallon. You're adding less than a fifth the amount needed to optimize Molly health. In other words, you're not doing much of anything. Plain vanilla sodium chloride ("tonic salt" or "aquarium salt") as opposed to marine salt mix (what you use in a brackish water tank) only raises salinity, which has some therapeutic value in terms of nitrate toxicity. Marine salt mix contains carbonate salts that buffers the pH and raises the carbonate hardness, improving the stability of conditions in the tank, and this also helps Mollies dramatically. Bottom line, you cannot safely keep Otocinclus with Mollies: to create conditions that Mollies need for maximum health and longevity, you need to add more salt than you're doing now, and that would be harmful to most freshwater fish, including Otocinclus. Trust me on this: I literally wrote the book about brackish water fish! Cheers, Neale.>

Re: Oto Catfish and brackish water? 05/18/09
Thank you much! I'm going to put some more salt in and look into the Nerite snails... Thanks again
<Good-oh. Nerites work well in brackish water, especially Clithon species; these eat a lot of algae! Cheers, Neale.> 

Re: Oto Catfish and brackish water?  05/23/09
I went to my LFS and they didn't have any of the Nerite snails... They just had "mystery snails."
<Not Nerite snails... Apple snails (Pomacea spp.)...>
I was told that they ate algae, but they were just sitting on the bottom.
<Eat some algae, but hopeless algae-eaters in most aquaria, being happier eating plants or fish food... also very difficult to maintain in the long term. Most specimens die within a year; need a resting phase in cooler conditions for 2-3 months per year. Generally fiddly; leave in the shop, or at least read up on Apple Snails first, e.g.:
http://www.applesnail.net/ >
I was able to test how salty my tank was and it was > 1.000 I'm not sure what that means...
<Nor am I; "> 1.000" simply means more saline than pure water... but that includes the sea! Apple Snails not tolerant of brackish water, so not an option for the Molly aquarium. You're after a specific gravity ("SG") of 1.002-1.003 for Mollies; see WWM re: Brackish water fishkeeping:
http://www.wetwebmedia.com/BrackishSubWebIndex/bracsystems.htm >
I could add more salt and keep looking for those snails.
<Don't buy the Apple snails for this system.>
Just wondering: do Oto cats tolerate that?
I know they can be very picky when it comes to water parameters... What do you think is best?
<For Otocinclus, you want low to middling temperature, around 23-26 C; you want soft to moderately hard water, so 5-10 degrees dH is about right; and pH 6.5-7.5 is fine. Water turnover should be medium-high to high, so say 6-10 times the volume of the tank in turnover per hour. Water should be clean, and the tank well established. Green algae MUST be present in the tank, or else provided via substitutes such as algae wafers; Otocinclus DO NOT eat diatoms (the golden brown algae on the glass); hair algae; brush algae; thread algae; or blue-green algae. They are not compatible with Mollies or other fish that want hard water, let alone brackish water. The majority of Otocinclus sold die a few weeks after purchase simply because their needs aren't met. If you don't have the right tank for them, don't waste your money!>
Also, I was told that the Nerites were hard to find ??? Is that true?
<Not even remotely true in the UK; most good fish shops have them, for around Â£1-2 a throw. In your own country may be different; consult fishkeepers in your area. By far the best algae eating snails.>
Sorry for throwing all these questions at you.
Thank you so much
<Cheers, Neale.>

Otocinclus Hello Bob, have heard a lot about you from folks at SDMAS here in San Diego. <Maybe see you later tonight> My gig is working on breeding marine ornamentals but I saw your article on the "little suckers" in FAMA and thought I'd use the excuse to introduce myself. I had never head of the fish until a few months ago, I helped a friend set up a fresh water planted tank and came across them. Gotta say I love 'em. I have a small backyard pond (300 gals) and was wondering how they might do in there. Temps are in the high 50's right now, but I thought as spring came on I could introduce some, maybe twenty or so. Do you think they could handle So. Cal. temps year round if acclimated? <Not all year round, no... could be kept outdoors maybe four, five months out of the year... but would insert a thermostatic heater... set low... for safety's sake> I've got some small Koi and pond comets (no surprise) but what stuns me is that there are a number of zebra Danios and white clouds that came in with "feeder" guppies I threw in there during the summer. To my surprise the guppies died out as the weather got colder in December but the zebras and white clouds seem fine! I know you're a busy guy but if you have a moment let me know what you think. ...David <These are tough little minnows. Have had them outdoors (nearer the coast) in large enough, weather-sheltered ponds in San Diego as well. Be seeing, chatting with you. Bob Fenner, WetWebMedia>

Otocinclus Meals Robert, <Hi, EJ, Sabrina here tonight, instead> I read your article on Otocinclus on wetwebmedia.com. Thanks. <Glad you enjoyed it!  I'm sure Bob appreciates the thank you greatly.> A couple questions:  In your article, you mentioned that they need wood to survive.  What kinds of North American woods are acceptable for Otocinclus?   <Pretty much anything that's been *very* well cleaned and either sinks on its own or is weighted will do.  Check out your LFS for driftwood ideas.> What state should the wood be in?  Fresh, weathered, decomposing, etc.?   <Very well weathered - as in, no bark remaining whatsoever.  Wood that is decomposing poses a problem as it will decay in the tank and make a genuine mess of things.> What is a good brand of sinking pellets to feed them?   <Frankly, my personal favorite dry food brand is Hikari, but I rarely (if ever) use algae wafers to feed my algae munchin' dudes.  Algae based frozen foods (Ocean Nutrition's Formula Two, for one example) are a good prepared food item to offer.> Will they feed on other vegetables besides the spinach, Nori, and peas you  mentioned? <Blanched cucumber and/or zucchini, perhaps the soft insides of green beans.... some years back, my Loricariids always appreciated the asparagus that I refused to eat as a kid....> Thank you very much. <You bet.  Wishing you well,  -Sabrina> EJ

Question Re: Oto placement   12/10/06 Hi Tom, <<Hey, Sean.>> I have another question for you already. <<Let's hear it...>> I was at a major chain pet store today, and much to my surprise, they were selling Otos (Otocinclus) for $1.99. Since this is the first time I've seen them in my area, and that price is too good to pass up, I bought 3 (I read on WWM that they do well in groups). I have 2 tanks, and I can't decide which one they would do best in. <<The quarantine tank, Sean. (Being a little silly but I'll explain.) The store I buy my fish from, my Otos included, is, literally, a 'Mom and Pop' operation and won't sell their freshwater animals for the first two weeks after they take delivery, i.e. they quarantine them all. Saltwater fish are held for four weeks with cards posted on the tanks showing the dates that the fish arrived at the store. That said, I can guarantee that this isn't the case with your Otos. Point number one. Next, Otos are notorious for being difficult to acclimate. Wonderful little guys that they are, they're easily lost early on no doubt due to the stress of transporting, handling, lack of sufficient food and -- the big one -- means of capture. Because of their tiny size and naturally tangled environment, many (most?) of the Otos that reach the store have been taken in the wild using cyanide, or other chemicals, to disable them for collection. (I would be skeptical that 'tank-raised' Otos would be going for $1.99 each. Mine were $3.99 each which I thought was a bargain.) The upshot here is that these chemicals can remain in the internal organs of the fish either shortening their natural lifespans of about five years or leading to a much, much earlier demise. Darned hard on the Oto, to be sure, but if one is lost and picked at by another fish, it, too, may end up with contamination from the chemicals I referred to. Now, let's move on to your options.>> Tank one is a 24g tall/show tank, moderately planted, with a cheap "fizz tab" CO2 system. Its inhabitants are 4 Opaline Gouramis, Trichogaster trichopterus (2 are the gold variety), 2 paradise fish, Macropodus opercularis, 2 Ramshorn snails, and one common Pleco, who will be re-homed soon as this tank will be way too small for him (he's only about 4" right now). <<Sounds like a good choice, Sean. And, I appreciate your thinking regarding the upgrade for the Pleco.>> Tank 2 is a 5g, moderately planted, with no CO2. Its inhabitants are 1 Betta and 3 cherry shrimp. <<Could be a good option as well but, personally, I like to add some aquarium salt in with my Betta. Your Otos would 'tolerate' the amount of salt I use but I don't think they'd appreciate it very much.>> Both tanks have laterite and gravel substrate, a good amount of driftwood, and a pH just above 7. Neither tank has much of an algae problem, although both tanks have small amounts of green "spot" algae. Now, here's my question: which of these tanks would be a better fit for my Otos? <<As you may have gathered, Sean, I like the larger tank for your new pets. The smaller tank would likely work just fine but I'm not a huge fan of keeping Bettas with other fish. Just me, perhaps. Also, if you do decide to add salt to your Betta's tank down the road, and I do recommend this, it probably wouldn't sit well with the Otos if they were in the tank.>> Sean <<Enjoy your new fish, Sean. Tom>>

What do I do with extra Otocinclus?  5/30/07 I have a 5 gal. Eclipse Corner Tank on my desk at work. There were 2 Betta's (with a divider) in it, but when I added 3 Oto's from PetSmart soon after the Betta's died of tail/fin rot. I moved them to separate bowls, and treated them but they died. I figured it was the addition of the Oto's so I expected them to die as well. That didn't happen. They cleaned my tank of all algae, and I feared they would have nothing to eat because it seems they won't eat the algae flakes. So, I went to my buddy's Cichlid tank and traded all the ornaments (no, I don't know if this was a smart thing to do or not, but I did it anyway). It seemed, that this brought new life to the Oto's, as very soon after I spotted little white things on the front of the tank. When I realized it was fry, I shut off the filter. I counted about 12 fry stuck the glass. I turned to the internet for advice and found little. I put a baby sock rubber banded over the filter intake and turned that back on. Added an air pump for them. I fed them boiled spinach leaves. Well, a spinach leaf from a coworkers salad stuffed in a cup of hot water. They ate little holes in that overnight. I do a 50% water change weekly, and slowly suck out the leftover food every few days to keep the substrate somewhat clean. Now I keep exchanging plants with my buddy's Cichlid tank for food and they clean it overnight. There are now 4 or 5 baby's left and they are half the size of the adults and seem to be doing fine. My question is, what can I do with these extra Oto's? Can they go in the Cichlid tank? Isn't that too much hardness for a Cichlid? Or can I support 7 to 8 Oto's in a 5 gal tank? PetSmart told me that they stock the same sex in the same tank and sell them that way so this wouldn't happen. Well they screwed up and now I have these new guy's. What do people do with their new fish when they didn't mean or even know they would spawn? <Wow. This is quite an amazing tale! On the one hand, a 5 gallon tank is really too small for Otocinclus. As a group, Otocinclus are considered "delicate" because they need good water quality and lots of oxygen. In most community tanks, they tend to be short lived. But yours are doing well, so well done! Anyway, as to where to put the Otocinclus. I personally wouldn't mix them with anything other than, perhaps, South American or West African dwarf cichlids. The problems are multiple. Firstly, yes, they will not do well in Lake Malawi/Lake Tanganyika type aquaria. Such hard and alkaline water conditions will not suit them at all. Secondly, when kept with slow moving things like angelfish and discus they tend to suck the sides of the bigger fish, scraping off the mucous. I've seen this in my own tanks, with the Otocinclus rasping away on large gobies, creating nasty blisters. Aggressive fish like convict cichlids will simply hammer them to death. So ideally, give them to someone with a peaceful community of other small fish such as barbs and tetras. PetSmart cannot possibly sex Otocinclus so their advice there was nonsense. In fact, breeding Otocinclus is quite uncommon, so you've actually done rather well.> Tom <Cheers, Neale>

What is the best live plant for Otocinclus?  4/19/08 What is the best type of live plant for Otocinclus? I have two tanks, one 30 gallon and one 10 gallon. I just added two Otocinclus to the 10 gallon, which is 4 months old and has 8 molly fry, born two months ago. (As they grow, I plan to move them to a bigger tank and only keep 2 mollies in the 10 gallon with the Otos.) I appreciate your site. Thank you! <Otocinclus spp. couldn't care less about plants, so use whatever you want. What Otocinclus need is green algae (not diatoms and not hair algae). So provided you have 2 Watts per gallon upwards, plus lots of surfaces to grow green algae (rocks, plastic plants, etc.) they will be happy. Otocinclus spp. are not compatible with Mollies; their water chemistry requirements are entirely different. Specifically, Mollies more often than not need salt to do well and definitely need hard, basic water conditions. Salt will stress the Otocinclus, which need not-too-warm, oxygen rich water that is soft and slightly acidic. There's no overlap really between what the two species need to do well in the long term. Otocinclus are extremely demanding, difficult fish, and the vast majority of specimens die within months of import. Good luck, Neale.>

Re: What is the best live plant for Otocinclus?  4/19/08 Thank you for your help. I will separate my Otos and my mollies. I am very new at this, and I obviously have a lot to learn. :) <Glad to help. There is indeed lots to learn, so buying a book before buying a fish is always good advice. Remember, the guys in the pet store mostly want to make sales! Good luck! Neale.>

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