Delicate, efficient and safety. Made of high quality crystal glass, high brightness, acid and alkali resistant, free from corrosion, flatness is good, no water ripples. Planaria trap comes with 1 holes and 3 holes design, which is able to trap planaria efficiently to reduce planaria population in fish tank. Planaria trapped inside the tube will never able to come out from the designed hole. Trap/Catches Planaria, Flat Worms and Leeches.