It could be, but they don't look like the ones I had. Mine were less 'hairy' with only 4-5 tentacles around the top. There's another organism that looks like hydra. I was trying to find the thread that listed it, but can't find it ATM. If I can dig it up I'll get back to ya.
If the shrimp aren't affected by them I'm guessing it might be the moss animals. I was watching my shrimp interact with the hydra. Whenever a shrimp bumped into a hydra, there was an obvious sting that shocked the shrimp. It didn't appear to be detrimental to the shrimp, but it was obvious it bothered them.