I had a 7 inch oscar in my tank and introduced a 10 inch oscar in to my tank to give him/her a friend. I think the new one is a she. The minute i put in the new oscar the old one got kind of upset and with gills wide open he rammed the new oscar constantly. After a day odd enough he was actually very protective over his new friend. But here it comes, yesterday i saw them both sitting in a corner all bruised and thorn apart. They keep locking mouths for several days now and look like crap, both bruised allot. They dont eat as much anymore either. Are they trying to breed or do they hate eachother? What am i doing now? I dont want to end up with a dead oscar. I absolutely love them both.

firstly, welcome to the site.

whenever a new fish is introduce in an existing tank, new comer
is always treated as intruder, that why it always prone to bullying.
however, since it is bigger to the existing, it will muscle up
to establish who is the boss... while the existing will try to
defend his territory.

only you can decide to rehome or give them separate tank.

welcome to the site


now paul has you covered on behaviour when a new fish is introduced into an established tank.
as to if theyre breeding or fighting its hard to say from your description. how big is the tank you have these oscars in and are there any tankmates with them? it could be a space issue but knowing some info it can be hard to know for certain what is going on.

Thanks for welcoming me guys. The tank is a 150 gallon and they have a few 3/4 inch tankmates. It should be more than enough room for them. I will wait a few weeks and see whats happening. If the fighting continues i might have to remove them. But one more question. Whats the shaking of the tail mean. And he moves his head in short abrupt turns as well?

Hi joker
My albino does the tail fin vibrating thing dont think thats a problem. But i think its defiantly a territory thing their going through especially if their both male.
good luck