I always kept a pair of blue gouramis around that I could move into a tank with hydra - they had it cleaned up in a couple of days, though I learned to keep them in the tank for about a week to keep any resting hydra from reinfecting - supposedly licorice and croaking gouramis also do a great job, and they don't get near as big as the blues - Flagfish also do a decent job, but they might also take out your plants

Update,

After adding 4-5 small pond snails to my 55 gallon tank.  Almost all of the water Hydras present have been eliminated after three weeks.  To give a descriptive visual on how bad the infestation was: one side of the tank the forward glass looked like a silicone wave of hydras over 2/3 of the glass surface.  Literally there were multiple 1000's of hydras were present.  Now after looking at the same glass with a magnifier, I barely can see any hydras.

I want to thank everyone for viewing this post and making suggestions.

Jim Langan, AKA Webmaster

Hello Everyone,

My water hydras are undetectable now, I'm sure some linger somewhere in my 55 gallon planted tank, however, all hydras apparent on the glass are now gone.

I hope this helps,

Jim Langan, AKA Webmaster

Justin,  this is heavily planted 55 gallon aquarium, I think Pancur C. would hurt the plants.

Thanks though!

Jim Langan

I've always had good results clearing hydra with just a pinch of flubendazole powder/10 gallons. This dose did not seem to affect Malayan Trumpet snails nor harm any aquatic plants. If there is a single hydra present in a tank of fish being fed live brine shrimp nauplii you will soon be over run with hydras. (Also works great to treat velvet).
See JAKA article by Charles Harrison, Ph.D.Ph.D.http://www.inkmkr.com/Fish/FlubendazoleArticle.pdf