My pacman tank has mites. They're small, about the size of a grain of sand, ivory colored, have smooth rounded butts, and seem to double in numbers every time I look in the tank. They congregated on the fish flakes I stuck in there to feed the little baby crickets, but now that the fish flakes are eaten, they're spreading out through the tank, and some are congregating on top of Lump's head.There's a little pile of them between his eyes. I heard that they aren't harmful to frogs, but I don't like the fact that they've chosen his head as their new hangout. How do I get rid of them and keep them from coming back?