I know this stuff works wonders on flatworms. I currently have an outbreak since I've started feeding my corals heavily. I just cleaned my garage out and came across an old box of salifert flatworm exit but it expired back in 2011. Sucks because its practically new. Anybody ever use it past the expiration date? Let me know what you guys think. Hopefully its still good, cuz this stuff is $$. :/