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I work in a public aquarium and while I care for all of the exhibits in my department, the freshwater native tank is "my tank".

Recently, we had a group of fish donated that were added to the exhibit, and among them was an . (Being a catfish fan, I was pretty excited they let me put it in the display, as my boss was adamantly opposed to catfish in there.)

This is a small exhibit, just a 6ft, 200 gallon or so? I had measurements, but I seem to have misplaced them. Currently it houses two spotted gar (both 10 - 12 inch?), a bluegill (full grown), another sunfish (supposedly a redear, but probably misidentified by the previous owner - 4 - 5 inch?), and the A. serracanthus (4 - 5 inch). This being a public aquarium exhibit, water quality is kept pristine. All fish can also be relocated or traded to other facilities if they outgrow the tank. Tank stocking is a little bit different than that of home aquariums.

The tank is fairly bare. There are a few pieces of driftwood (no great hiding places in them though), rocks that I stacked into a couple small caves for the cat, and some fake plants. We have yet to see him eat anything (which may in part be due to the types of food offered - if he doesn't eat the usual diet tomorrow I'll be bringing him a sampling of my foods from home).

So far, the bullhead has been shredding the fins of all the other fish, especially the gar, which were the only existing fish in the exhibit before the group of other fish were added. The sunfish and cat had all lived together previously. The bullhead will swim up and taste the other fish a bunch, then nip a fin.

I know bullheads are not exactly docile fish, but we can't allow him to be tearing up his tankmates. My supervisor has threatened to dump him into a crocodillian exhibit if he keeps it up.

Is there anything I could be doing to curb his aggression? Will the fish work this out once they're used to each other or will he bully them to death? Is there any chance I'll get him to stop or is it hopeless? This is a grogeous fish, I'd hate to dump him into an exhibit where he may never be seen again (no underwater views with our crocodilians).

EDIT: On further reading I may have jumped to an ID too quickly - seems more likely this is the mottled Florida variety of .

@Victor Jarikov, any thoughts?

If I was given this stock as a prospective one, I'd probably be more concerned for the catfish and not concerned for the sunfish or gar. Gars have a tendency to bite anything that moves, regardless if they can swallow it, on the condition that the party being bitten is timid.

So this is a bit surprising but not out of the realm of possibilities. This is a "natural" exhibit but not a natural situation for the fish and hence it is ~always a gamble.

***Is there anything I could be doing to curb his aggression?

Having had several specimen of the southern brown bullhead, I can't say I noted any kind of territorial aggression towards a plethora of other natural and unnatural tankmates I kept with them. Neither do I recall reading that they are aggressive in my general readings. This makes me think this is hunger. Or a learnt habit from its prior tank(s), where it could have been permitted to prey on tankmates or at least supplement its diet with slime, scales, and/or fins.

My first guess is that when it starts feeding, it should subside. So I'd say to try and get it to feed asap.

***Will the fish work this out once they're used to each other or will he bully them to death?

IMHO both are possible (the whole thing's a gamble as stated... any such tank is IMHO and all my tanks are such) but the latter is highly unlikely IME. The size disparity also makes it unlikely. The preferred location in water column does too.

***Is there any chance I'll get him to stop or is it hopeless?

If I was forced to be quantitative, I'd say 90% is you can stop it (or it will on its own) or bring it to a tolerable level.

If this continues after it starts feeding well, we can think what else to do out of the box as I'd think this fish is rather an exception than a rule. But everyone's experience varies however greatly or slightly.

Lowering the temp, if an option, may change things too. The temp will start dropping soon seasonally anyway, so time's on your side.

(Eric, never was notified. Of course, you misspelled my name slightly, maybe that's why.)

Viktor Jarikov wrote:(Eric, never was notified. Of course, you misspelled my name slightly, maybe that's why.)

Yes that's exactly why. The @ notification must be letter-for-letter correct or it won't work. I was so focused on spelling your last name correctly and getting capitalization correct, that I ignored the first name. Sorry Viktor.

Cheers, Eric

I would just add...make sure it is a serracanthus, often the southern mottled form of nebulosus is mistaken for a serracanthus.