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Do We Overfeed Our Fish?

Over-fed (and likely egg-bound) Black Phantom Tetra

My answer to the above question is “Yes, I often have overfed my fish”.  I want them to grow and be healthy!  Yet when I thought about this question recently, it seemed that I might be doing them a disfavor.  Active species of fish must be quick and fast, and storing excess fat would be detrimental to their survival.  When fish appear truly obese, they are often eggbound or have internal diseases such as dropsy, cancer, etc.  As a result, many species of fish are not capable of storing a lot of fat, and excess food simply passes through unutilized, creating greater waste.  This greater waste creates problems in a confined environment (our aquariums) by being toxic and inhibiting further growth of the fish.  Frequent water changes are a big help, but how many of us can do them religiously?


The “cardinal rule” for beginners is to feed as much food as the fish will consume in 5 minutes.  Often in 5 minutes fish will eat large amounts of food and become very distended in the belly.  This time limit may eliminate the uneaten food, but does not address the excess waste the fish will produce from overeating.  When we feed just moderate amounts of food each feeding, the digestive process is more efficient, and most nutrients are utilized, not thrown back into the aquarium as undigested waste.  It seems that club members who get the fastest growth on their fish feed lesser amounts, but more often.  I now try to feed amounts of food where the fishes’ belly just begins to show getting larger, then stop.  This can be hard on some slow feeding species, but they should be in a separate tank anyway.  By trying to feed more than once daily, the fish will get the same amount or more food, but less toxic waste will be produced.  If I don’t get to feed twice that day, the fish will be fine, if not better off.  In Nature, fish often go for long periods of time without eating, and have no ill effects. 


The quality of food is a big factor in health and nutrition of fish.  Live foods are the best and probably the mostly efficiently digested.  Frozen and dry foods likely produce more waste and we should be more careful with them.  Even with live foods, however, their most efficient use would be to spread out their consumption.


Tank cleanliness is important in keeping pollution levels down.  I like to use snails and “bottom pickers” for this task like barbs and goodeids.  Catfish are slow eaters and will allow other fish to gorge themselves before they get adequate amounts of foods.  For this reason I think catfish will do better in a “slow eaters” tank, and the other fish will benefit from not being overfed.  One sign of overfeeding is when the snail population of an aquarium explodes, indicating you are feeding too much.


Getting good growth from your fish is important and an indication of good health.  In the past, I was not getting as fast growth as I would like, but could not figure out why.  I was feeding once daily as much as the fish would consume.  Although my water changes were not as frequent as I would like, they seemed adequate.  Whenever we would take a vacation, I had a neighborhood youth come over to feed them daily.  Only small scoops of dry food were instructed to be put into each tank daily, which was considerably less than I would normally feed, as I did not want them to be overfed.  Each time upon returning, it seemed that my fish grew a lot more than I would normally see in a week that I was feeding them.  It finally dawned on me that my excess feeding could have produced more growth-inhibiting waste than the lighter feedings, and that they had actually grown more with less food!


I feel that overfeeding our fish can often result in “killing (or harming) them with kindness”.  I am trying to feed my fish less food at a time, but it can be difficult to change habits and concepts.  Some of these feeding concepts possibly could be transposed to Humans, but that would be a whole other article that might create considerable controversy!