It is an anemone...of what kind who knows. You shouldn't be scooping up random creatures and throwing them in your tank. Florida has laws around that. And this isn't even putting into effect you don't know what it takes to keep your mystery anemone alive...
Because you don't know what it is, you don't know what it eats, you don't know how to take care of it...oh, and it is illegal to take creatures like that out of the ocean in Florida.