I would verify this before you take my advice, but from what I have heard, tulip anemones don't have the regenerative capabilities that aiptasia have (meaning they won't grow back or propagate themselves from small pieces). With that in mind, you should be able to just scrap them off with a razor blade or something else that will let you physically destroy the anemone. I tried this on a couple in my QT tank and they never came back. That said, I don't know if it would be the best method if you have a ton of them (because of fouling the tank and the amount of slime they release when you do this). Again, I would definitely verify this if you are going to do it in tank. If they're QT'd (as it sounds like they are) maybe just give it a whirl.