My oscar recently attacked my Jack Dempsey and left deep abrasions along one side of his body and he seems to be recovering well because of the nice water conditions.I now call him "Scars".I figured maybe the JD was getting a little too comfortable in the area my Oscar dug out for himself and my Oscar retaliated on him.I assumed it was normal behavior,Until yesterday when i found my pleco torn to shreds.It is a decent sized pleco so im sure he wasn't thinking it was food.The pleco was about 4 inches in length.I think my oscar is getting aggressive because of the temp change.

It is very cold here and the water heater is barely keeping the water temp comfortable for the Oscar.The water temp is around 76-78 when i usually keep it at a comfortable 84-86.

Im not worried about the JD or the other small fish i have in the tank because i really doing give a damn about them and i can get new ones but i just want to keep my oscar comfortable and to stop killing fish!

I have the answers to some of the questions you might ask.

I feed him pellets and Chiclid food,with an occasional batch of goldfish every 2 weeks or so.

The water is in great condition(very clear)..with regular tests to make sure the ammonia levels and such are normal.

I feed him 2-3 times a day(pellets and flakes..(morning,afternoon,and before bed)

I dont usually change stuff around in the tank.maybe one every 2 weeks(mainly because the fake plants get dislodged and float near the top when he gets aggravated)

other than that..id like some options.

I don't want to sound like I'm chastising you but any fish somebody owns should be cared for properly. If that's not possible, find a new home for it.

Anyway, it just sounds like aggression to me. Some Oscars are aggressive, others aren't. Luckily, I've never had a serious aggression problem with my Oscars and I have got various cichlids living in harmony. If you have gotten an aggressive Oscar that is going to attack other fish, you need to keep it on its own. Jack Dempsey's can be very aggressive in their own right so are normally okay with the Oscars. So that's all I can suggest really, if you don't want your Oscar to attack other fish, don't keep any other fish with it.

Man oscars r unpredictable! i never had any aggression problem because i have only 1 oscar with a common pleco, at first my oscar used to attack the pleco when they were small, but now the oscar doesn't bother the pleco, they became friends.........

how big is your oscar?

My oscar is about 7-8 Inches.Bulky too,its obvious he swims alot.Ill post some pictures soon.

To the other guy,i take care of my fish properly.I take care of them all equally and i make sure they are fed well and healthy.Theres a difference for not caring about the other fish as much as the oscar,and not properly "taking care" of them as much as the oscar.With oscars,you have a bond with them because they are smart and they are cool to have.Other fish are pretty much "Fillers" to make the tank look not so empty.