I found this, maybe it can be helpfull.
Leeches
These external parasites are visible on the skin, gills and fins of the fish and are similar in appearance to Ick.
Since they attach themselves to the fish, the best method of removal is a bath in a salt solution for 20 minutes (dosage 2.5 % salt to water). During the bath, most of the leeches will simply fall off; the ones remaining can be removed with a pair of tweezers.
Copper sulfate has been used to successfully remove and control less harmful worms. Over time, copper has been found to do more damage than good concerning the overall balance of the aquarium. The side effects of copper are rarely in relation with the possible benefits.
How to build a worm trap
Next to commercially available worm traps, it is fairly easy to make one at home. All that is needed is a plastic container or jar with a lid.
Using a razor blade or sharp knife, the lid is cut in X shape. The corners are then pushed slightly inward to form an opening in the lid. The size of the opening varies, depending on the size of the creatures to be trapped.
For the trap to work properly it is important that the worms do not see the "bait" but rather smell it. The container should therefore not be transparent.
For bait, clam and shrimp meat can be used as well as any fish meat available. The bait should be prepared in a way that is small enough for the worms but just short of being mashed up totally.
The container is then placed in the area where the worms are suspected and kept there over night. Adjustments to the size of the lid opening and the bait source can be made for optimum results.
Edit: I have read that turning the tank water slighly brackish, will eliminate the leech problem, how that would work with your fish I don't know though. Leeches can supposedly come from feeding live foods, plants and intro of new fish (think you would see it on the fish though), so I will now have starring competion with my tank, making sure I don't have them, pretty horrid-looking thing. Almost makes planeria look cute compared to this!!!