I have two Oscars and have had them both for 3 months. I introduced them to the tank at the same time. About a month ago, I noticed terrible marks on both fish, as if they were fighting each other. After doing some research and going back to the fish store, I was informed they were most likely mating or flirting. Now, a month later, I have just noticed that only ONE of my fish has those same marks. I'm not sure if they are still mating or flirting, or if the one is attacking the other. Any thoughts????? Please help

How big are the fish and how big is the tank they're kept in?

The smaller fish, with all the marks, is about 3". The bigger fish is about 3.5" The tank is a 55 gal. The smaller fish comes up and eats when it's time, and the bigger one doesn't bother him. THey used to swim right by each other all the time. THe last day, I've seen the small one in a corner by himself, although this morning they were swimming together again.

oscar become sexually mature between 12-16 months. so if your o's are 3" or so i dont think they're mating yet. they could be establishing dominace in the tank. i would keep an eye on things and see what develops.

also a 55 is small for two oscars. you will be ok for awhile but eventually you will need a bigger tank.

I definetly know that I will need a bigger tank shortly. THe people at the pet store also told me they were to young to mate, but could just be "practicing" or flirting.