Fighting Goldfish

Question
I recently received a 2-gallon hexagonal aquarium, when i went to PetCo they said that 2 small goldfish could live comfortably in it, i purchased 2 comets.  They have been in the tank a week and a half and have suddently begun to fight, one seems quite dominant, am i dealing with two males or could there be some sort of chemical imbalance that is causing this?  I initially thought it was a territorial thing, as there was one cave-type tank decoration, i put a coffee mug in the tank and that made them happy for an hour or so, then the chasing began again.  Should i simply consider giving one away?

Answer
Hey Michael,

I know that at petco specifically store policy is 3 gallons per inch of goldfish, so whomever told you that needs a report to management. That's unexceptable behavior on the employee's part and I'd ask to speak to the specialist.

Typically, goldfish wont fight unless there is some sort of severe problem. Goldfish are normally regarded as completely unaggressive, and my concern at this point, is that one is either pregnant, or very ill. I'd recommend at this point taking them both back, and asking the department specialist for fish more suited to your tank.

I'm terribly sorry for the ignorance of that store's associates! And i hope you can find fish more suited to your tank type and care needs.

Best wishes, and good luck.