Eliminating hydra without killing the other inverts

I found a bunch of hydra in my smaller grow out tank today(not surprising, as everything in it including the substrate, is straight from a local lake). Anyway...is there any way to eliminate hydra without killing off all of the other more desirable inverts? Or..am I just stuck with them?

Hey Paul,

If they were recently collected and with other inverts from the wild, I've found that their numbers tank very quickly. I think they only become problematic when they're the only consumer available (nice analogy for what's going on in the Great Lakes )... Rotifers, for example, are probably better at handling population booms and busts in food resources in a biodiverse system than hydra. The hydra just have a bad name because they're really good at population explosions without interspecific competition. And they're big, and they'll sting your fry.

Todd

I recently went through the same thing. The ones I had were very small and a very pretty green color. After some googling I learned the green color was from symbiotic algae just as with coral and anemones. This explained why they clustered on the sunny side of the tank. I also learned the algae supplemented nutrition for the hydra and thus they were not such voracious preditors as some of the bigger, nastier hydras. Before I learned all that I had tried to eradicate them with a razor blade and siphon. Once I learned more about them, I decided to let them stay as they were cool. That's when I learned what Todd just told you - they peter out quickly with limited food supply. Now mine are gone.

Todd,
Are they really that much of an issue with fry? What size fry are we talking?