i only feed mine frozen blood worms (if your getting them at wal-mart, they are only $3 and are kept in tiny, tiny cups, and are not fed many die, and they have never carried diseases with the ones ive gotten (4) however the albino ones at wal-mart are actually clawed frogs, and when they get bigger, might kill smaller frogs and fish)
the normal colored ones dont eat fish, or kill each other, they are skinny, but plump right back up once they are fed
i would only go 4-6 as well in a 10 gal
they also really only like frozen blood worms (which is actually cheaper per ounce compared to freeze dried) and they love it when you break off a chunk, put it close to their face, and they make pigs of themselves
remember, only the regualr adf are fish safe, not the albino clawed frogs, which grow much larger