Depending on what is living in your tank you might be able to dose it with fenbenzadole, a dog dewormer that sells under the names panacur and safeguard. Done properly (google for specifics, but it's 0.1g/10 gallons of tank as I recall) it won't do anything to fish, arthropods, or snails, but will kill virtually anything worm-y. I don't know of anyone using it on leeches specifically though. I'd rather trap/squash them myself, but if that doesn't work out or if you find that they've infested your tank, it's an option.

Depending on what is living in your tank you might be able to dose it with fenbenzadole, a dog dewormer that sells under the names panacur and safeguard. Done properly (google for specifics, but it's 0.1g/10 gallons of tank as I recall) it won't do anything to fish, arthropods, or snails, but will kill virtually anything worm-y. I don't know of anyone using it on leeches specifically though. I'd rather trap/squash them myself, but if that doesn't work out or if you find that they've infested your tank, it's an option.

Oh, I forgot to post an update to this topic. The evil brown leeches are all dead. But anyway yes, I did buy some levamisole HCl and had it on hand, ready to dose the tank if chemical warfare became necessary. Thank you for the suggestion.

Edited by EricaWieser, 08 June 2011 - 12:25 AM.

I did squish one just now. Ew. I'm going to trap them too, though, because I bet it's like it is with cockroaches; if you see one, there are actually a lot more.

Update:
I checked the trap this morning and the shrimp was still inside, untouched. There were some snails on the outside of it looking wistfully at the entrance they couldn't get in, but that's about it. I wonder if I killed the only leech by squishing it yesterday. Or if there are more in there but they just didn't take the bait. Or if they would take the bait if given another night or two. Hmm.

Not sure if I ever clarified or not, but it's not like cochroaches. There was just that one leech. I guess they only emerge when they're out of food. So in the end all my trap making was for naught.

Edited by EricaWieser, 15 February 2012 - 03:14 PM.

i really cant stand leaches... besides the fact that i have often had to pull them off my legs, i saw one i cought out at lake waccamaw that actually grabbed a small fish and attached itself to the inside of its gills, quickly killing the fish. i was still in the lake collecting, the fish was still in the bucket. granted, the leach was almost as big as the fish, but since then i have not trusted them. it really was a sickening site to behold. i wish you luck in getting rid of them. and if you do find a good way of trapping them, keep us posted. im sure ill run into the same problem eventually.