An Automatic Feeder

Inspired by Dr. Ronald Shimek's article on upside down viewing of feeding in the February '03 issue of Reefkeeping, I started to think of a way to continuously feed my reef tank. I came up with a simple and (so far) functional solution after having spent much time thinking about many complicated, and probably expensive, solutions.

I simply use a 1000 ml polypropylene jar (Nalgene), placed in one corner on top of the tank, fitted with a small homemade bulkhead (a drilled nylon screw with grommets and a nut) connected to a silicone tube that delivers water just below the surface of the display tank. Inspired by the more advanced "Geosapper" device featured recently here in Reefkeeping, I inserted a bent acrylic tube to control the surge volume into the bulkhead. From a powerhead in the overflow, I insert a t-fitting at the output and reduce one of the outlets to fit a 2 mm silicone tube. The small silicone tube feeds the jar with tank water (about 2 drops/ sec.) When the water level in the jar has risen high enough to overcome the backpressure from the tube connected to the bulkhead, it empties about 100 ml into the tank. This happens about once every hour. To ensure enough circulation and oxygen in the jar, I have connected an air pump as well. In the figure I have indicated the tube dimensions that work for me after a lot of experimenting. Note that the small (2mm) silicone tube easily gets clogged and needs to be cleaned at least once a month to secure a steady flow into the jar. As an alternative to help prevent clogging, a peristaltic pump (dosing pump) could be used.

I first made the set-up to feed on a drop-by-drop basis, but discontinued that configuration when I saw that the dominant Chromis was watching the feeder's outlet continuously and was chasing all the other fish away from the food.

At present, I use this device to feed Artemia nauplii (filtered out from a separate hatching cone) and Nannochloropsis occulata (instant algae), both added once or twice per day. I have also tried the device with dead adult Artemia but with limited success, as the nutrients get washed out and the Artemia tends to sink to the bottom of the jar. As the fish tend to loose interest in the repeated feedings of Artemia, perhaps the ideal food for this device would be something like Golden Pearls of various sizes, but with lower a nutritional value and some sort of capsulation. I suppose that a thick gelatin coating would reduce the leaking of nutrients before the food is captured and eaten by the animals.

It's my opinion that this device has reduced the amount of undigested food, and subsequently improved the water quality in the tank. However, many other parameters have changed during the same time period, so it is impossible to address the improvement only to the new feeding regime.

As an alternative one could use a jar with a bulkhead at the bottom which would be connected to a silicone tube that goes through a time controlled valve like those Sirai produces (http://www.sirai.com/inglese/serieP/2vie_NC/2v_ncM.html). This jar should be filled in the morning and emptied during the day (no tank water input). This would probably give the same concentration of food from the feeder throughout the day, in contrast to the set-up described above which delivers more and more diluted concentrations of food.

This feeding device works well with live food such as rotifers, brine shrimp and phytoplankton (dead or alive), but it can also be used as a dosing device for many additives. I thought of it primary for feeding my reef tank, but it would probably also work well for a rearing tank, delivering a more continuous supply of food for the fry.


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An Automatic Feeder by Vidar Jensen - Reefkeeping.com