yep oscars are one specific fish that doesnt grow to the size of the tank you may have to get a bigger tank shortly as they will grow real big. i wanted some for my 4 foot tank but was scorned for even having thaught of it. firemouths are fine in a two foot tank imho i had two in a two foot tank with betas and neons and stuff a while ago and they where fine. but i think perhaps yea its the oscars that are the problem here