Leeches! ugh! Help!

I've heard copper is a bad idea, and that it stays in the tank forever. yikes. It would probably work, but I'd rather strip the tank down before going that route. So far the salt seems to be working (sorta). They are dropping off some of the fish but not others yet. I need to up the salt dose a tad and wait it out I guess.

Thanks!!
 
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