The zebra loach Botia striata grows to about three inches long, so nowhere near the size of clowns! I've kept them quite happily in a three foot tank
They're a very nice fish, I've never had any trouble with mine
I've never seen any of my zebras nip anything, although I haven't kept them with angels myself. I find it very unlikely tbh.
I find the zebras are very playful & seem to like chasing other fish around, they do look like they have little nips at some of my rosy tetras, but I've seen no damage caused/