[SueM]

I get them by the handfuls from the river bank here. They are awesome for filtering out algae and microbes.
I have about 10 in my turtle tank, without a barrier. They are happy as clams (sorry bad pun) living off the crumbs the piggys make when they eat. The turtle tank is in a direct 70% of the day sunny window and not 1 spec of algae. He doesn't try to eat them, but he will push them around like basket balls for fun, but they just slap shut & wait till he's done.
And yes, for you paranoids out there, I do quarantine then with a few feeder fish for 3 months.