I have two Oscars in a 55 gallon. I use to have a dragon fish in with them, it disappeared. I just took my sucker fish out becaue one of my Oscars "the Grouch" Has started to bite at his tail. This has just started, a couple days ago he went off food. He will suck it in chew and spit it out. I have tried his favorite shrimp, and silver stripe fish. He doesnt even eat his pellets. As far as behavior he seems to bite at the glass, doing alot of rearranging, and "kissing " the other fish. Should I be worried? What should I do? They are about ten inches long. He still gets very excited when I goup the tank, he doesnt act sick at all!! P.S. they are tigers...

Welcome to the site. Unfortunately, 55 gallons is two small for two large Oscars plus other fish.

The behaviour you mentioned is quite normal for Oscars, especially a pair of Oscars. Whether you have a breeding pair is hard to say, he would only know this if you saw them laying eggs.

All of the behavior you mentioned is normal for O's. If you provide some hiding places for your sucker fish you may be able to return him to the tank. Although I have to agree with Oscarfishlover that tank is too small for two 10" O's plus other fish.