major flatworm help needed.

[karazy]

here's the issue.

ive got flatworms.They are in my sump, fuge and main tank. Ive tried using flatworm exit twice. first time i put in the normal amount and turned on the carbon reactor in about 5 minutes.
i wake up and there are still some left. i decided after hearing some opinions that i didnt leave it in long enough or didnt add enough.
so the second time i try it i dose enough for my 40 gallon system, and wait half an hour. almost all die, but there are still some left. i siphon them out, but within ten minutes more appear.
so, half an hour after the first dose i for another 40 gallons. same result.
so, after an hour of starting dosing, i add another dose.
still some left. these fricken things are invincible. and ofcourse by the next day they are full tilt reproducing again.

so my question is, what can i do to completely kill every single flatworm?