Can someone tell me if this is normal? My oscar lives in a tank with a plecostomus. They have been tank mates for almost a year now. We have had other fish but they have gone missing...we eventually found the fish we had were not good mates for the Oscar. Recently my oscar has been fighting with my plecostomus and I am not sure why. He will attack him out of no where and then will start swimming face first into the bottom of the tank and twitching all over. This normally lasts only a few minutes and then he is calm. I am concerned about this behavior being so new and unlike my fish. We have an extremely clean tank and he is eating Hikari Cichlid (what the pet store recommeded). He eats very well actually and does not look like anything is wrong (no scars, swollen eyes, discoloration, etc.). Someone please help. I am not sure if this is normal, if he is mad or is in bad health. I don't want to lose my oscar.

Welcome to our community

I really don't think you've got anything to worry about. The behaviour you have described is something I've seen on numerous occasions with my Oscars. I don't know how big a tank is but when you mix large fish, they can't exactly avoid each other and this is when aggression can start, especially if they are of a different species.

Do you test your water? If you haven't done it in a while, I would advise you to test for ammonia, nitrite, nitrate and pH. The fish can on occasions act strange affair toxins present in the water. However, I think your Oscar is just being an Oscar.

My field of expertise is no where near as advanced as OFL but i would just like to add that OFL is most certainly right and my Oscars behave exactly the same when i introduced my Silver Dollar in to the tank. They had an understanding about who's part of the tank was who's and most of the time the Silver Dollar would respect that but when he crossed the line perhaps at feeding time the Oscar would behave similar to yours. Showing basically who's boss really and she would also behave in strange ways by dive bombing the tank and sometimes just having an out of the ordinary 5 minutes:laugh: But as we all know it's not out of the ordinary to an OScar to display these displays of Boisterous-ness:P As OFL has rightly said doing some simple water tests is invaluable in finding out if anything else is to blame...I wouldn't worry too much though it's just an Oscar thing!

smith209 wrote:

which one is attacking which? if the oscar is the attacking, then it is normal, trying to establish territorial dominace; if it is the plec attacking, then you are in trouble, he is hungry and love the taste of oscar's body slime. you have to watch out for night splashing of oscar, plec will attack the oscar while sleeping.

as OFL had said, water parameter is needed to evaluate your concern further.

Watch the plec. If he seems to be getting injured (e.g. torn fins) you need to separate them.