Planaria Trap Leech & Flatworm Trap / Catcher for Shrimp Tank or Aquarium by Awesome Aquatic. Glass 3 Hole 11.3 cm ( 4.5” ) x 2.3 cm ( 1 “ ) round, 8 hole 3 x 3 cm ( 1.2” ) round cylinder Funnel Design to let the critters in but not escape. Natural burrowing habit of the planaria, leeches and flatworms drive to investigate the baited trap. Partially burying the trap, holes in the substrate, so they move straight in it from the gravel. This method can possibly speed the process of catching. Drug and chemical FREE so there is no harm or residue from its use. 100 % will not impact water quality. Set it and forget it until tomorrow for an easy, very hands off way of trapping the unwanted critters. Add your Normal aquarium food as your bait and watch it work. Clear Glass ( 3 hole style ) or Plastic ( 8 hole style ) so not to intrude or be an eye sore in the tank or aquarium. This also makes it convenient to determine when it needs to be cleaned and rebaited. The smooth surfaces make rinsing out and cleaning a breeze.