I use to just dip and that bit me so now I quarantine everything. I've found numerous things get through initial dipping including spiders, red bugs, black bugs, predatory crabs, aefw and Monti eating nudibranchs. All of those made it through Bayer/Coral Rx so now I still use those but I invested in quarantine tank just for new corals. Call me paranoid but I also quarantine everything else I get for 3 months as well, snails, crabs, algae you name it it all goes through.