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Fish/how many fishes in a tank


I'm having a few questions about pet fishes.i'm having a freshwater aquarium with some golds,sharks,silver far things are good.

1.At which condition we can say there are too much fishes in a tank?
2.what are the effects of having too much fishes in a tank?how its related to their growth?

Hi Mick,
  That isn't a simple question.  As a VERY rough rule, people say something like 1 inch of fish per gallon of water.  So you could have 10 1-inch fish in a 10 gallon tank.  That said, you could not have 1 10-inch fish in the same tank.  How many fish depends on many things like the activity of the fish, how well they get along, how much structure (plants, wood, rock) you have in the tank, how much filtration you have and how frequently you do water changes.

  You should be changing 25% of the water once a week, every week to keep your fish happy and healthy.  If you do not do enough water changes, then nitrogen products build up in the tank, and that stunts growth, or worse.  

-- Ron C.
  Cichlid Research Home Page <>


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Ron Coleman


I am an expert on cichlid fishes, particularly New World cichlids. My broader expertise includes the behavior, ecology and reproduction of fishes in general. (I am NOT an expert on Goldfish). Please do not use abbreviations, such as "my GT has a swollen eye" because I don't know what a "GT" is. The more clearly you can explain your question, the better chance I have of understanding what it is that you seek. I keep fishes both as a scientist and as a hobbyist and I currently maintain about 140 aquariums.


I am an Associate Professor at the California State University, Sacramento in the Department of Biological Sciences, and I run a website, called the Cichlid Research Home Page . I also write for many popular aquarist magazines, and I was editor of Cichlid News magazine for several years. I am a scientist and I spend my time teaching fish biology, ecology, behavior and evolution and doing research on the reproductive biology of fishes, particularly cichlids. I do research in the laboratory and in Costa Rica, Nicaragua and Mexico. My main interest is understanding the evolution of parental care in fishes. I am interested in encouraging greater public awareness, understanding and participation in science.

Cichlid News, Tropical Fish Hobbyist, Freshwater and Marine Aquarium, Science, Behavioural Ecology and Sociobiology, Copeia, Canadian Journal of Zoology, Trends in Ecology and Evolution, AUK, Environmental Biology of Fishes

PhD (Toronto, 1993) MSc (Simon Fraser, 1986) BSc (British Columbia, 1983)

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