Aggressive Discus

[glstine]

I always thought discus were supposed to be very peaceful fish. I added three new discus to a 30 gallon planted tank containing 1 discus. Whenever I feed the old discus chases the new discus all over the tank and nips at them. I took him out and stuck him in a 10 gallon tank for a week. I put him back in and he continued with his aggressive behavior. So I took him back out for two weeks and put him back in and he is still doing it. When not eating, all is fine. I try placing food in multiple locations in the tank and he'll be eating in one place, see one eat at another location and go attack him. I don't know what else to do. When I isolate him, he won't eat so I'm afraid to isolate him for to long.

[loganj]

Discus are cichlids and cichlids almost always have a pecking order. I have even seen angelfish get nasty when a new fish is added although it is not their normal behavior. Can you rearrange the tank? Sometimes this will give the new additions a chance to establish a territory and disorient the aggressor enough that he will leave the others alone. Add the aggressive fish last. It may be something that you just have to wait out if the rearrangement doesn't work.
Logan J