[Peter Finke]

Different species of Hydra are efficiently killed by Flubenol, the small green ones for instance that sometimes appear when feeding is based on Artemia. Take a very small quantity (a tip of a knife) only, put it on the water surface, do nothing else and the Hydrae will contract in a few hours time and disappear completely within the next 24 hours. I never saw any negative effects on my fish and their offspring. I cannot, however, give a guarantee in respect to very small young. But if they are four weeks old it should be safe, especially if there is a water change of three quarters afterwards.