FWexit has worked for me, temporarily though. I used it once and it nuked them all, or so I thought. No problems at all, but I siphoned out all I could see and then dosed the tank. When they were all floating I sucked them out too. Looked as if they were all gone, but about a week later I noticed they had come back. I have since does a second time doing the same thing and then followed it up the next day with a stronger dose. After those two back to back treatments I still see the buggers. I guess I will have to dose it again. I have read to double the second or third dose so I may try that. There are not very many in there, less than 5 from what I can see, but if I can see 5 then I know there are more.
I kind of think they are becoming resistant to FWE, but who knows?