Aggressive Gibbiceps?

[brianfl]

I have a large gibbiceps (18") in one of my ponds outside. He seems very aggressive when I put other catfish in there. I tried two leiarius pictus (about 7") and at a different time one a auchenoglanis occidentalis. Each time the gibby chases them constantly. Both times, I put the others in my other pond. The pond is 8 x 8 x3. I also have some fantails in there and he doesn't bother them, it seems just other cats. Also, we have a number of wild guppies and he doesn't even acknowledge their existence. I didn't think gibbys were all that aggressive. Anyone else seen this behavior?