I know of one species, Pelteobagrus (aka Hyalobagrus) ornatus that only grows to around 2" and is active/visible by day. They're social fish, prefer live or frozen foods and well-planted tanks. Not bottom dwellers at all, they're upper-mid water fish, quite mellow and good tankmates for gourami's or bettas.
Otherwise, Synodontis petricola or lucipinnis (very similar in size and appearance) are also smaller fish, around 4", that also do best in groups.
Overloaded with endler's and BN pleco's, PM if you want some shipped.