Do your things look like the picture I have attached below? If so, then they are definitely hydra. And hydra are something you absolutely don't want in a shrimp tank, as they will kill baby shrimplets, and will annoy (sting) the adults, which will be a source of stress to the adult shrimp.
Unfortunately, mere physical removal of the ones you see is probably never going to be enough to totally remove them from the tank. Your best bet is to treat the tank with either liquid or powder form of fenbendazole.
In powder form, you dose at the rate of about 1/10th of a gram per 10g of water. Dose, wait 48 hours, dose a second time. Problem solved. Kills hydra (as well as planaria, nematodes, and other such critters) in the tank but is perfectly harmless to shrimps. You can get fenbendazole in most pet stores (usually in the dog section, as it is sold as a dog de-wormer) or online. It is sold under several brand names, I think Panacur is the most common. I bought some powdered Panacur about a month ago on ebay for under $10 shipped, in order to treat one of my shrimp tanks that had hydra due to me putting plants in there I got from someone online (and, unknown to me, had been kept outside).
If you do a Google search for "fenbendazole" and "shrimp tank" you should get a lot of hits that discuss it at length.