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About Ron Coleman
Expertise
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.

Experience
I am an Assistant 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 am editor of Cichlid News magazine. 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.

Publications
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

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

You are here: Experts > Animals/Pets > Pet Fish > Fish > Cichlid kills new cichlids

Fish - Cichlid kills new cichlids

Expert: Ron Coleman - 10/30/2009

Question
We began our 20 gallon cichlid tank about 2 months ago with 3 cichlids. We do not know the specific species-- one is orange and black, another is dark blue with a yellow tail, and the 3rd was bright orange. The bright orange one died within a month or so, but did not seem to have been attacked--we thought perhaps it was bloat. Then we added a light blue, but vibrant cichlid, which was slightly smaller than the other two. It held its own for a while, then I noticed it was not eating like the others---it would eat if the food happened across its path, but it wouldn't seek out food on its own, so the other fish would usually finish all food well before it had time to find "Blue" as we called “it” (we have no idea how to distinguish the sexes with any certainty.) Within a couple days of the original change of eating behavior, I noticed the orange and black fish do a shimmy in front of Blue, so I thought maybe they were mating, and then the next day Blue had barely a tail fin. I removed Blue and put it in a vase with water from the tank and it was dead within 12 hours. I'm afraid to introduce any new fish because it seems that the 2 we have are EXTREMELY aggressive. What the heck happened? How can I prevent this in the future?

Answer
Hi Erin,
Your two fish have claimed that tank as their territory and it is very likely that if you put other fish in there, they will meet the same end as "blue". There isn't really a whole lot you can do about it, other than getting a larger tank.   You can try adding a lot of structure (wood, rock, plastic plants, etc) to divide up the space, and then it is more likely that a newcomer would be able to survive. A single plant or rock, however, is not going to do it. You need a LOT of structure.

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>

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