brown bullhead CAN max out at around 21" however i have yet to actually see one near that size in person. But, if taken care of properly, be ready for a good 15" or so fish. I would say at least a 75 for life, bigger is better though. Make sure there are hiding spots like a cave of two also. I have to say, they are my favorite fish. Can be quite active especially at feeding time, and will eat out of your hand. They are like all other cats, they will eat pretty much anything as long as its edible and it can fit in their mouths. With that said, i usually fed mine when younger, mysis shrimp, krill, bloodworms, earthworms, and when older you can add larger things like shrimp, squid, pellets (floating or sinking), algae wafers, quarantined feeder fish, chunks of fish fillets, crickets, and meal worms. These fish are absolute gluttons, monsters trapped in a smaller body, enjoy your fish.