I was having problem keeping snails alive for 8-10 months. I was finding pyramid snails on my turbos, but wasn't finding them on any of my trochus, ceriths, or nassarus snails but they seemed to still be dying. One night when I was looking in my tank after the lights went out I noticed one of my trochus snails flipping itself back and forth like they do when they flip over so I grabbed a flashlight and found a giant polyclad flatworm about 3-4" trying to cover it. I immediately grabbed a turkey Bastet and blew it off the rock and removed it. I tested some PraziPro on it and it killed it in minutes. So I ended up removing all my feather duster, coco worm, and Christmas tree worm rock and put them in quarantine and treated my entire SPS reef tank. I left the medicine in for about 2 hours, then did a 50% water change and threw carbon in, and did another 50% water change the next day, my reason for the water change was to reduce the impact on the worms in my sand bed. I returned all my ornamental worms after a week and had no noticeable negative effect on the worms in my sand bed. It's been over a year and I haven't seen a polyclad flatworm since and very rarely lost a snail anymore, pyramid snails are still there but not causing any major problems and I remove them manually when the snails are easily assessable.