THe mantis is fine ICK need a fish to host it. Inverts and rock will not host the parasite but the eggs can lay dormant for a while. so tank should be devoid of fish for up to 6 weeks. but the next time you get a fish it can come in on that fish. so at this point I would not worry about catching the fish to QT them treat them and feed them where they are as the stress of catching them could be too much for them at this point. They have had the ICK for a while already. just feed them garlic and selcon for the next 2 to 3 weeks every day and then every 2 -3 days there after.

Bill

its only been 3 days for the harlequin tusk and the lion had it 3 weeks ago but right now just the tusk is showing any ich