hydras and guppy fry - help!

This morning I noticed a hydra in my tank. It's pale-yellow, 2 mm long with
six tentacles. Now it seems the more I look for them, the more I find - some
are really small, less than 1 mm, some are larger. I even saw one sting a
snail when it got too close.

Anyway, the problem is, I have a breeder net in the tank with guppy fry of
various ages (about 20 in total). The fry seem to be all right, although its
pretty hard to count them.

It's a 20 gallon tank with live plants. Besides the fry, there are also a
pair of guppies, 5 neon tetras, 2 rasboras, and 1 rummy nose tetra.

One article on the net says hydras are no concern for livebearer fry - is
this true? If not, how do I get rid of them? I don't feed live food - just
tropical fish flakes. Is it a better idea to move the fry to another tank?

Please help, I really don't want to lose the fry.