6 tips to introduce new fish to the aquarium

Hello, community of

How many times did we change the water and the aquarium or plane were destabilized, some or all of the fish died. Here a number of causes. . . . . . . . . . .

1.- Temperature increase too fast (Changes with hot water).

In the blood of the fish, gaseous bubbles are formed, which can cause an embolism (obstruction of the blood vessels) and therefore death from the so-called bubble disease. Fish, on the other hand, and contrary to what is popularly believed, withstand a slight decrease in temperature, as happens every night, in their wild habitats and in our aquariums. Even in the majority of species it stimulates the disposition for reproduction, because when noticing the addition of fresh water and consequent decrease in temperature, together with the agitation of the organic matter that occurs when the water is poured, they identify it with the time of rains and instinctively start the zeal. In general, the temperature difference should not exceed 3є C.

2.- Alteration of the ph.

If the value of the ph., Is diverted too much, towards the alkaline zone, by the change of water, the ammonium dissolved in it will be transformed into toxic ammonia.

3.- Drinking water taken directly from the tap.

Being subjected to a pressure of several bars, the tap water contains too much dissolving air, we can see it when we first fill an aquarium and see the bubbles that form in the glass and objects. When this pressure is relieved, the excess air is released, distributed in the form of innumerable gas bubbles throughout the aquarium, including the gills of the fish, where they cause serious respiratory disorders and in acute cases death.

4-. Copper poisoning

It is known that hot liquids have a greater capacity for dissolution. When we use, hot tap water, as a rule, it has acquired a temperature through a home heater, which in 90% of the cases has resistances composed of said metal and that dissolves as the water passes. Another case is the dissolution of copper in water, in domestic networks equipped with channeling, by copper pipes, which fortunately are less and less used. Because in certain circumstances and depending on their concentration, they can cause the death of the bacterial colony of our filters, and later of plants and fish. The effects of copper are more toxic the more acidic and soft the water.

Therefore, we must avoid using hot tap water and even if it is cold to let the tap water run to eliminate possible high concentrations of the pipes.

5.- Too strong changes in water values.

An excessive modification of the previous values ​​of the water (Ph., Oxygen content) due to the change of the same one, can cause the death of the leaves of some aquatic plants, especially of the cryptocorine.

The higher the water temperature, the lower the oxygen concentration.

Well with this simple information, we can make changes without endangering our organisms.

Greetings to all members of this forum.

Print News
Send News
PDF version
related links
· More about The Aquarium
· Other news published by Elfishdecuernavaca

modules.php? op = modload & name = News & file = article & s>

The aquarium and electronics © 2015 website created on January 17, 2001 updated September 2015


Before you even buy the new fish, you must have set up your aquariumIt is important that you do it in a place away from external sources of cold or heat and the windows, since direct sunlight generates undesirable algae, you can take a look at other tips that we give you when mounting your aquarium.

Before buying the new fish you can also investigate a little about the type of fish you want to have, or ask the store manager when you are going to buy your aquarium, as it is logical the size of the aquarium you have will determine the size of the fish that They can live inside. The type of fish you have must have similar temperature, hardness and water pH requirements, and if you want to have different species, they must be able to live together.

Once you have the aquarium in the ideal place, you must have all the necessary equipment to maintain a healthy ecosystem such as filtration, lighting, heating and water chemistry.

Let the filter work for a few daysThere are many options to choose between internal, external filters and backpack, the type of filter you choose will depend on the size of the aquarium, the available space around you and your personal preference. Here are some tips that can help you decide what type of filter is best for your aquarium. By letting the filter run for a few days you will be able to verify that it works correctly and it will move the surface of the water ensuring that the water is oxygenated correctly.

  • Temperature

There are heaters with preset temperatures, usually at 26º, and other aquarium heaters offer the option of choosing the desired temperature as is the case of the Fluval M Series. Again, the temperature at which you should set the heater will be according to the needs of the new fish you want to introduce. In addition to the heater it is important to have a thermometer that tells you the actual temperature of the aquarium, and so to know if the heater is doing its job correctly, check the temperature daily. Like the filter place the heater a few days before so that the water temperature is correct for its new inhabitants.

Do not worry, you should not have extensive knowledge in chemistry to have an aquarium, but it is important to have some clear concepts:

pH: It measures the acidity or alkalinity of the water. It does not have to be at a specific level, but within a range. You should make sure you choose fish that have similar pH needs. To help you measure the pH and know if it is correct, there is a parameter measurement test, such as the one offered by the Nutrafin pH Test Kit.

Here are some examples of species and the pH range in which they can live:

  • Viviparous: from 7 to 7.6
  • Rasboras: from 6.2 to 6.8
  • Cardinal tetras: from 6.2 to 6.8
  • South American catfish (e.g., coridoras): from 5.8 to 7
  • Melanotaenides: from 7 to 7.4
  • African cichlids: 7.8 to 8.5
  • Goldfish and Japanese carp or Koi: from 7 to 7.5
  • South American cichlids: from 6.2 to 6.8

Ammonia, nitrite and nitrate: all of them are chemical compounds that are produced in the normal cycle of an aquarium, through the decomposition of organic matter such as non-ingested food and fish waste. The difference between them is that they are more or less toxic to fish in high concentrations. In the so-called nitrogen cycle, ammonia, which is the most toxic, is degraded to nitrite (less toxic) and finally to nitrate (even less toxic). For this process to take place It is very important to have nitrifying bacteria to do it and Fluval offers Cycle bacteria to help us achieve it. Pour the correct dose of Fluval Cycle into the water a few days before bringing the new fish to create a sustainable environment in your aquarium and prepare it for your new tenants.

Chlorine and Chloramines: Although in many places we can drink from tap water, this does not make it suitable for housing fish since it has harmful substances for them such as chlorine, chloramines and heavy metals, luckily this is very easy to solve : simply by throwing the right amount of water conditioner into the water, we recommend Fluval Aquaplus, which also has herbal extracts to reduce fish stress.

Hardness of water: we say that a water is soft if it has a lower concentration of dissolved salts in it (especially composed of calcium and magnesium), and we say that a water is hard if on the contrary it has a high concentration of dissolved salts. In general to have healthy fish and plants the water hardness should be between 70 and 150 mg / l, but the acceptable level may vary depending on the species. To know the level of water hardness there are also measurement tests such as the Nutrafin GH / KH Test Kit. If you need softer water, you can use the Fluval Granulated Peat or dilute the tap water with osmosis reverse water.

It is important to provide light to your fish so that, as in their natural environment, they have a day / night cycle. But lighting is even more important if you have a planted aquarium, since to favor the growth of plants you must use a lighting designed for it. If you do not have an aquarium with plants or you have plants with low light requirements such as some anubias and microsorium, we recommend the Fluval Eco Bright low consumption LED lighting or the Fluval Aquasky LED climate lighting, in addition these two LED screens have the RetroFit system to be able to place the LED screens on T5 and T8 fluorescent tube screens.

3. Acclimatize them to the water of your new home

Then, pour some water from the aquarium into the bag with the new fish, about a third of the volume of the bag. We do this to get used to the chemistry of the water in your new home, which although we have prepared it to be the one you need, this may be something different from the water inside the bag. We wait about 10 minutes.

Then we repeat the previous step by throwing another third of the volume of the bag and wait another 10 minutes.

For most tropical fish this is enough to acclimatize, but it never hurts to ask at the store if they have any other method or advice that can help you.

Then you can use a net, glass or other container to finally remove the new fish from the bag and introduce them into their new habitat.

Do not introduce the water from the bag into your aquarium. Introducing unknown water into your aquarium can cause diseases to be transmitted.

5. Relaxation and coexistence

To help them relax, turn off the aquarium light. If you already had fish in the aquarium, turning off the lights will cause them not to pay full attention to newcomers. We also recommend taking the recommended dose of Fluval Aquaplus, to reduce the stress of newcomers and those already living in the aquarium.

If they are the first inhabitants of the aquarium you can wait about 24 hours before feeding them, but if you already had fish in your aquarium feed them as usual.

Aquarium weight and configuration:

A quick account to know the weight of your aquarium is to know that a liter of water is equivalent to approximately one kilo. For example, a 300-liter aquarium with a 150-liter sump is roughly equivalent to a weight of 450 kilos in water alone. To them we must add the kilos of rock, the weight of the structure and the urn. The simplest way to tackle the problem of weight is try to get as much water as we can, keeping it in buckets or holes large enough as to be able to also remove much of the aquarium rock.

Appearance of the aquarium practically empty and disassembled. You have to be careful what rocks or corals we choose to take out. The base rocks that support the entire aquascaping structure are recommended to leave them intact if possible.

As for the configuration of the aquarium, we must assess the most fragile or mobile parts of the structure that supports the aquarium. For example, steel structures are very resistant and they can be pushed from any point, but the wooden structures are more fragile and pushed from a bad place with the aquarium not too empty can lead to breakage of the table. We always recommend Push wooden tables of aquariums from the lowest possible point.

Important is also to have assessed before if the The new location of the aquarium is viable for this purpose..

How much help do I need ?:

Normally, the emptying of an aquarium can be done by a single person, needing help from someone else when the rocks or internal structures of the aquarium are too heavy. But when moving an aquarium (usually pushing if the floor allows it) we will need more people. A good proportion would be one person per 150 liters of aquarium. If the aquarium is going to be moved piece by piece it would be advisable to ask for help from a professional because of the delicacy of manipulating the glass of an aquarium. Having help in these cases can avoid unnecessary efforts and scares.

Time is one of the most important parts of this process. We must take as little as possible for the well-being of the aquarium inhabitants, since this task puts them under great stress. When you remove rocks, coral pieces, plants or delicate fish from an aquarium, you start a countdown in which the temperature and oxygen of the container where they are placed will begin to decay little by little. For this case, it is helpful that the cubes where we take the living beings are the largest, so that the temperature falls more slowly. An oxygenator on hand can help us keep the water containers well aerated. All appliances must be unplugged at the right time. The only equipment that will help you in this task will be the light screen to be able to see correctly throughout the process.

Large cubes with corals and invertebrates that help us reduce the weight of the aquarium for its displacement.

Although the procedure should be performed as quickly as possible, it is also not good to tie the blanket to the head and not measure your steps. One of themost tricky tasks when it comes to emptying an aquarium is to get part of its content, since a bad movement with a blunt rock can lead to a disastrous blow against any of the aquarium crystals ... normally, reserve all Saturday morning, just in case the flies!


Keep in mind where the aquarium will be moved and leave the area clear. Calculate the amount of buckets and containers you need to take out the water. If you are going to move the aquarium by car or van everything gets more complicated. You will take more time, you will spend more effort and you must ensure that the transfer is safe for the aquarium and its inhabitants.

One last note:

It goes without saying, and it is no less important, that the aquarium will enter quarantine immediately for at least a couple of weeks after the displacement of the aquarium. Throughout this period we will limit ourselves to observe the behavior of its inhabitants, verifying that we do not have white dot buds and that the plants or corals are still healthy in their new location.

Do not introduce any new living being in the aquarium until we are sure that the system has already stabilized again. If no water change has been made, consider doing so in the days after this process.

Water change in the aquarium

Water changes in the aquarium are essential in maintaining our aquarium so that our fish can survive. Although we have a filter (good or bad), it does not clean everything and it is necessary to make water changes from time to time so that it is in optimal conditions. I guess now you're thinking, so what do I have the filter for? because very simple, if you did not have it, you would have to change part of the water every 2 or 3 days and with it you only need to do it every month (although it is advisable to do it every week or two weeks).

Well now let's get to the core:

When should we change the water for the first time?

If we have just assembled our new aquarium, we must wait approximately 50 days until the first water change. During this time we will have it with water, cycling (about a month). After that time, we can put our first fish and when about 50 days have elapsed since we rode it (30 days cycling + 20 days with fish), we can change the water for the first time.

How is it done?

  1. In a new bucket, we let "tap" tap water for 24 hours to evaporate the chlorine. If it is cold, it is advisable to put a water heater so that the water we pour is at the same temperature as the aquarium. There are "water conditioners" that serve to pour directly into the water that remove chlorine in a few minutes. They personally seem like a loss to me>

How often do you have to change the water?

If you are a beginner, it is better to change 20% of water a week or every 2 weeks as we will control nitrates better. When we already know how to control them, it will be enough to do it every month although if we do it every week the water will be more crystalline.


  • The bucket to change the water It has to be used exclusively for aquarium water. It is not worth the one we use to scrub because it has traces of soap, bleach, etc ... and is toxic to fish. You have to buy a new one for the aquarium.

  • Get link
  • Facebook
  • Twitter
  • Pinterest
  • Email
  • Other apps


The use of anti-chlorine or water conditioner is not only to eliminate chlorine, heavy metals are also neutralized and some chloramines that are very harmful to our fish that do not go away with evaporation, also add colloids to protect the mucosa of the fish . If the water is from the net (not from a well) I think the conditioner is mandatory, because the net water is suitable for human consumption, but not for our fish. Otherwise the article is fine.

Should I take the fish before adding it to the water?

The conditioning (dechlorinated, etc.) of the water is done in a separate container, never with the fish inside, and you have to wait for the additives to agree and neutralize the toxic elements for the fish, after that you can put it in the aquarium.

Good, I have an aquarium for a little while, it is about 50 liters and I have goldfish, I was wondering how to know if nitrates are good, I wait for your answer.
Very interesting your blog has helped me a lot. Thank you

Buy a nitrate test, you have many brands, I use one of Sera and it works quite well.

My guppy fish sink by shaking their heads and the next day they wake up dead. I don't know if they are sick or if it can be contagious. Help to

It is for the quality of the water, also check the temperature.

It is clear that something happens to them. Do you have any other symptoms?

My fish looks very sad, I have some corydoras and they spend it all the time down for about a week and they didn't act like that and a zebra just died. I would like to know what happens?

The corydoras are usually always in the lower part of the aquarium, it should not be a bad indicator. It is true that when they are flirting there are races between them and they walk all the time up and down, but this ceases and they remain calm for seasons.

Good I am new to this I have a 100l aquarium and I would like to ask you a question.
I have the aquarium without heater and the water rises between 30 and 30 degrees and a half of temperature that I can do to lower the temperature of the aquarium without affecting the fish

You must buy an aquarium fan, the temperature should not exceed 27 ° or lower 23 °

You can buy a cooler. They sell them for about € 30 depending on the size of your aquarium. If you are near a window, lower the blind in the hottest hours.

hello, today my son, my golden fish woke up "dead", I took it out of the water, passed it to new water and began to move, after about 5 minutes it stiffened and died, but notice that several of its scales had fallen He was with me for almost a year, but I do not know if what happened to him is contagious because only on October 28 I was ragged 7 more fish, but he was fine until we got them together, would it be that he was already sick? Or did he get sick from the other 7 who brought me? please

It could be that they had a disease the rest and have been infected, although it seems too fulminating. Are the rest sick? How often do you change the water, let it sit before 24 hours? Hot or cold water fish? There are so many variants that answering you is very complicated.

Hi. The "goldfish" I imagine it was a carassius. These types of fish are quite gregarious and if any of those who gave him something "hyperactive" must have besieged him and hit him to death (the best explanation of the scales). Always, before entering new fish we should check its compatibility sheet first. It could also be a disease but I doubt it since it was too immediate.

I'm going to buy an aquarium, but the water in my city has a lot of chlorine. Would it be worth using bottled mineral water?

If the water quality is not good and letting it rest is not enough, you can buy conditioner to remove chloramines and leave the water ready for use, I tell you that because that will be worth it.

Hello, how are you looking 20 days ago among my brothers we bought little fish, they are three oranges, but today I went to feed them in the morning, note that mine did not move much like the other two, the question is dancers and They are very playful and because today I did not see anything jugfueton to mine and I do not know what happens to me today is 20 days am and tomorrow morning I will make the water change
I really don't know what happened help me

Are they cold water fish? Did you cycle the aquarium before putting them in? With the data you give me, I can tell you that either the water in your aquarium is not in proper conditions or they have not adapted well to the aquarium. Tell me your aquarium water data so I can help you better (temperature, ph, hardness, nitrates.) Greetings

Good, I have an aquarium of 200 liters, and I make the change every week of 2 buckets of water. I made a product of the recommended dosage mercadona. And I am realizing that every time I change the water I have some loss. With the siphoner, I slow it down. I have about 50 fish and hot water, and here in this town there is a lot of cal. Someone advises me something THANK YOU.

Hi José Angel,
We let the water rest in the buckets for 24 hours to remove the chlorine and pour it directly into the aquarium. Our advantage is that the water in our area is of good quality and lime and chloramines are not a problem. From what you say, it does not seem that the conditioner works very well, try to change the brand if only by letting it rest one day you see that it is not enough.

Hello, I have an aquarium 3 months ago, the water has not changed since it is clean and I have never had any problems until today that two of my fish are swollen and the scales bristling, the tail and fins as bites can it be? I add that I have a small shrimp help xfavor

From what you tell us, they seem to have dropsy (we have an article about it:

Soon you will have to make a minimum change of water, because although you see it clean you should make measurements of nitrites, nitrates and ammonia to see how the water quality is going.

Anyway, those fish that you have told me say goodbye to them, because I do not think they will go ahead with what you are telling me. I'm sorry

For dropsy you have to separate them and leave them without eating approx. 5 days (the fish can live on average 2 weeks without eating), on the sixth day you grab half a house previously boiled and smear it with olive oil and the days. That should help to evacuate, and when you feed your fish you have to soak the food beforehand, and don't give them much because they keep eating.

Thank you very much for cnt so fast joo what a shame it really gives me the others are great, and e separated in another fish tank! What food do you recommend? Greetings and thank you

Geacias x cnt so fast joo what a shame it gives me! You give me some advice about food and water change periods and such! My aquarium can have approximately 30l thanks a greeting

We used to give them freeze-dried food (scales, granules, etc.) and we realized with the experience that it was not the best as usual food.

For a few years we have given them different frozen foods, we let them thaw first and then we supply them to our fish without pouring the water that the defrosting gives off. Its half-life has increased markedly. I recommend it to you.

Regarding water changes, in this article you have a guide of more or less what you could do. Having 30 liters you can change a little more than half a bucket, once a week or every two weeks and you will be fine.

Good week ago I bought my aquarium and the water is very cloudy I have already died 4 fish and take the water to a store and they tell me that it is ok, I do not know what to do change or not the water can help me Thank you

Hi Michael, if you bought the aquarium a week ago, it is normal for the water to be cloudy since it is cycling. During the first month, which is what lasts the cycling of water, you can not put fish because they die. Water change can only be done after the first 50 days. What you must do is return the fish that you have left to the store (they should give you the money back because they should not have sold you) and wait for the month of rigor to pass the first fish. I recommend that you visit the section of the blog dedicated to first timers with aquariums and that we have called BEGINNERS. I assure you that even if you started off badly, if you finish the cycling successfully it will be the beginning of a good ecosystem for your aquarium.

I have a fishbowl but today I changed the water became cloudy in a matter of hours. I want to know what I did wrong .. I can't see my fish anymore.

Hi Angy, you give little information so we can help you. Is your aquarium new and cycled? Do you usually siphon the gravel? Do you have gravel or sand?

I am new at this. I just bought a 100l aquarium and I would like to know the steps to follow to cycle the water well since I have read many things like taking a few drops of ammonia. throw food (scales). every day throw away the abtibacteria.
Thank you!!

www.http: // There you have a few answers to your doubts, when you finish the article you will see that there are A few links at the end, look at how to set up an aquarium that puts you some more things. Cycling time you know that it is about 1 month regularly.

I am a beginner, I have today a 100l aquarium (I currently have a 20l with 8 fish, 3 tetras, 3 guppies, 1 bullet shark and 1 panga).
I wanted information since I read a lot about cycling and I would like to do it well. I have read about dropping ammonia drops. food (scales). leave it without light (led) for at least 1 week. which has to be spent after 25 days and not all at once (current fish).
I wanted to know the best steps and if mixing my fish can be a problem.

I would try not to throw all the fish at a stretch. If you can do it in at least 2 or 3 batches 7 days apart.

hello help please I do not have antichloro but I want to know if I can use bottle water those that I bless of 500ml please help I do not want anything to happen this month was a very important gift please help me it will only be the water for one to 2 days to go for the antichlor fish are gol fish

We let the tap water rest in a 24-hour bucket to evaporate the chlorine and that is great for us. The water in our area is good, we don't have chloramine problems, so we don't use antichloro.

Yesterday I changed my water, we love fish and I forgot that I solp, I had to change half of the water and I changed it all and my fish are now swimming upstairs taking air puffs that I know that helps, I don't want to lose my fish, I have them for a year

Max, I don't understand you. Have you taken all the water from the aquarium and refilled it?
That water that you throw into the aquarium you let it rest or you put antichloro?


I have a fish tank, two betas, one red and one blue, everything was fine, and suddenly the blue went down from the fishbowl, it didn't go up almost red, it was ok the next day, the dead red swollen eyes appeared, I opened it and it had its little bell full of visitors white like eggs

I don't know if it will have anything to do with your case, but if you notice that all the fish are going to the bottom of the aquarium, the filter may have stopped.
If, in addition to the swollen eyes, the body was swollen with pineapple-like scales, it may be dropsy. We have an article with photos so you can see if it looks like something that happened to you.

Hi, can I take a 15-liter bucket out of my aquarium every month and put 15 liters of the tap on the floor for 24 hours? I also wanted to know if I can use well water, if the water in my field well has fewer metals and less ph me It comes better because here I have a very high ph, but I don't know how long I can keep the well water in bottles waiting a month to throw it into the aquarium.

We change every 15 days around 40 liters in a 180 liter aquarium. I don't know how the water in your well will be, the thing is that it doesn't have chlorine, that's why the rest. You do not have to wait a month to make water changes you can do it every week, but in less quantity.

Good morning! I am new to the subject of fish and 5 days ago they gave my mother two goldfish, I have a fishbowl but as one of them began to make bubbles and they told me that it could be for oxygen, so I ate a Fish tank and ox, I have several doubts:
-How long should I stop filtering the water from the new fish tank before adding to the fish? (In the store they told me that two hours, or is it better that I leave it longer?)
-the sand you buy is colored (blue), and hw had to wash it several times until he releases more color and the water becomes clear, is this color toxic to fish? Pasaria algo si aun suelta un poco de color, aunqe como he dicho, las he lavado hasta que no soltacen mas color.
-con respecto al agua, tengo que echarle un poco del agua en la que se encuentra ahora en el acuario? Lo digo por el tema de las bacterias, xq sólo tengo el acondicionador del agua que me dieron para echarle mientras se va filtrando o es mejor que compré también?
-como he comentado antes, tengo dos, uno que no estoy segura de que tipo de goldfish es, creó que es un abanico,y este es el que hace las burbujas, es más activo que el otro. Que por cierto las bur unas no las hacia hasta que añadimos al otro. El otro es un ojos de burbujas, y tiene la barriga un pelin hinchada como si hubiese comido mucho pero eso desde el primer día q lo tenemos , ya estaba así, eso es normal?
-Como puedo saber si es hembra o macho? Al igual que los betta estos también hacen burbujas como si fuesen nidos? O las burbujas es x el oxigeno? Porque ayer cuando cambie el agua de la pecera,(el acuario aún lo estoy instalado) dejó de Hacerlas
Esperó una respuesta

En primer lugar para realizar el ciclado del acuario se recomienda tenerlo 30 días, así que imagínate que buen consejo te han dado con lo de las 2 horas. Si le echas al acuario acondicionadores será lo que te ponga en las instrucciones de los productos que uses, yo no tengo experiencia de esa forma, siempre he esperado los 30 días de rigor. No sé si los goldfish son más duros y no necesitan tanto cuidado, eso te lo comentarán mejor en una comunidad de goldfish, nosotros no hemos tenido nunca.

- Que la grava pierda algo de color puede ser normal, haces bien lavando la grava un par de veces antes de meterla en el acuario. No debería ser perjudicial para tus peces, pero después de lo que te han dicho de ciclar en dos horas para echar los peces (en ese tiempo no le ha dado ni tiempo al agua a eliminar el cloro), no me da mucha confianza esa tienda.

- Desconozco como sexar las especies que nos has comentado, nosotros sabemos de otros tipos de peces de aguas tropicales un poco más cálidas.