are there any catfish small enough to keep in a 75.........or i was thinking of growing one out and putting it in my pond but i would still need a smaller one........so are there any smaller catfish species???
There are loads of cats that stay within a foot, many that stay within 6", unfortunately few of them are commonly available in your LFS/LPS.
Commonly available are members of the Acanthodoras (various Raphaels and etc), Pimelodus (various Pictus & Pims of all sorts) and Synodontis (of many many varieties).
May I suggest www.planetcatfish.com , I think they have a listing of species according to length, you can then go into the Cat-e-log and get profiles on'em.
Perhaps you can find some of the oddballs for sale at auctions or online ex/importers.