yes guppygirl, google tells me that I'd have to drain it for a week and treat with lots and lots of salt. Seeing as this isn't viable, I was hoping for suggestions. If you have nothing to helpful to add, please butt out.
have you got another tank.
I don't think a leech could live very long without a host. So you could collect your fish,plus any snails etc. ensuring they are leech free and move them for about 2 weeks and the leechs would have no food. If they are reproducing then the baby leeches are going to be hungry and without a host the hole generation would hopefully die effectivley ending the lifecycle in the tank. And saving your fish from a LOT of hungry baby leeches. Just my thoughts i hope they help.