From time to time, some of us faces pest problems. Hydra is a pest we don't want in our tank. There are discussion thread on how to get rid of Hydra, from snails to fishes, or even, chemicals.
Using Fishes - Galaxy
http://www.arofanatics.com/forums/sh...axy+fish+hydra
Using Snails - Pond or Apple Snails
http://www.arofanatics.com/forums/sh...ting+rid+hydra
Using Chemicals - Discourage
http://www.arofanatics.com/forums/sh...removing+hydra