When your fish start having parasite issues of worms, grubs and black spots in your fish fillets then thank your snails and waterfowl. As a general rule, the more snails that a pond has the more parasites that will develop in the fish flesh. Fish hatcheries consider the large mystery snail (trapdoor) a nuisance which is an indication of their overall benefit for a recrational pond. What the pet shop guy didn't tell you was he ment ""they are the best pond / aquarium snail...."" for lily ponds, backyard ponds and aquariums not recreational ponds. Few aquarium shop employees are well versed on the ecosystem functioning and ecological balance of plants, animals, and water chemistry found in fresh water lakes and ponds.
Last edited by Bill Cody; 03/14/13 02:41 PM.
