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Goldfish tumor
Goldfish tumor  
My tank is 29 gallon.  I have 6 goldfish that have grown to an average of 8 inches each.  Filter is an Aquaclear 70.  I don't know where to find a replacement bulb for my hood, so I am using a cheep light.  Needless to say, I have a nasty tank unless I change the water about every 4 days and clean the filter as well.  Maybe the bulb I am using is causing the algae (brown) problem, or maybe the tank condition could be responsible for my fish's malady.  I obviously need some expert advice on a few levels.  The photo below is not my fish, but a photo I found on-line that is very similar.  He has 2 of these tumors.  They are the color of his body and growing large...Thank You!!

Hi Valerie,
 Unfortunately I am not an expert on goldfish, but I can tell you that goldfish do get these sorts of tumors quite regularly.  There really isn't anything you can do about it because basically it is a cancerous growth. Many fish live a long time with such tumors.  

 That said, you really need to get a larger tank. You have a lot of fish in not very much water and that is not a good thing and could lead to even more problems.

-- 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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