I left the treatment in the tank for 5 days: 2 days longer than recommended, but necessary ,so I wasn't sure what to expect for collateral damage, I was very pleasantly surprised. I have 70 astrea snails, 20 nassarious, 3 emeralds, 70 blue legs, a serpent star, 2 tuxedo urchins and a few frogspawn, duncans, trumpets, favia, pectinia, shrooms, zoas, palys, sinularia, kenya tree, acan, blastos. The only casualty I suffered was a devils hand. Unfortunately my GSP survived in style. All CUC were unharmed. I did not do a water change yet as to leave some of the medication in circulation to finish off any stranglers, but I fired up the skimmer and loaded the reactor with carbon and purigen to pull out the organics from all the deceased xenia. I thought I was going to have to break down the tank, so I am stoked this worked out so well. Hope this was helpful.