ewww ok im not sure what these are called, BUT i have seen them before, every so ofton i go on fish trips and one of the times i was up there, i watched a good friend of mine pull one of these out of his customers tank, hes said there fine with somethings, but not all....i would pull it out just to be sure, ad im goin up to visit and learn more tomorrow, so i will ask and try and get more info for you