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Fish/Red tiger Oscar fish


My boyfriends red tiger Oscar fish has been acting weird we have like a skull in there and most of the time she hides in it we think she's pregnant but were not for sure she seems lopsided when she swims she's kind of leaning to the side or if she's at the bottom just sitting there she's kind of leaned over as well. We feed her feeder fish she's not over fed at all. The tank is well maintained its a pretty big tank for her she's by herself in it besides when the feeder fish are in there with her were not even sure if its male or female. She generally swims in one area which is around the skull but she mostly hides in it she doesn't swim as fast and she only comes out mostly when the light on her tank is out she seems mostly active when the lights out. So how can we find what her sex is? Also what could be wrong with him/her?

Hi Courtney,
  First, please realize that oscars lay eggs so they cannot be pregnant as such. It is pretty much impossible to tell the sex of oscars because the males and females look exactly the same. You can only tell at the actual time when they are laying eggs because the female's spawning tube is differently shaped than that of the male (his tube is more pointy).  

 As for what is wrong, most likely the problem is an internal infection caused by eating feeder fish. I strongly discourage people from feeding feeder fish to cichlids such as oscars because all it takes is one infected feeder fish.

-- 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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