How to fish with artificial worms?

How harmful are intestinal parasites/worms in fish?

• My LFS has been selling me fish with intestinal parasites for quite some time now. They admit that they catch the worms from their distributor, but the worms aren't harmful so they sell the fish anyways. I have noticed that all the fish I get from them seem normal and healthy, and stay that way until I treat them. When I treat them is when the stringy worms come out and they start to get sick and die. So I am just wondering, how long will the fish last without medication? Every time I medicate it does more harm than good, and the worms will never be completely eradicated. Would it be OK the introduce the fish with these 'harmless' worms into another tank?

• Answer:

  those worms are not harmless. they kill the fish. you should never buy a fish that has worms if you can help it and your fish store should not be selling them to you. do not mix healthy fish with fish sick with parasitic worms... or any sick fish for that matter.