i have a comet thats just about a foot long and for some reason he's became aggressive towards one, and only one of my goldfish, a black moor. And its not ok, he's started tearing up his fins (i have pictures if any cares to see..)

The comet is the biggest fish in my goldfish community but i've had him for awhile now and have never had a problem. Most of my goldfish are males, Im actually not sure about the black moor though.

Their diet is definitely just fine. The water temperature is at about 74.

I've had goldfish for years and i've never seen this.

Male aggression? Food aggression? Space??

I will admit the comet should most likely be in a bigger tank but i rescued him from a 28 gallon tank when i worked at a petstore and i haven't been able to find something better for him.

Anyone know?