Aiptasia are polyp-like creatures found in marine aquariums, usually introduced with corals or live rock. They can harm corals by outcompeting them for space and food as well as looking unsightly.
NT Labs Marine Anti-Aiptasia disables adult polyps rapidly, denying them the chance to reproduce. Firstly, use Anti-Aiptasia to target the largest Aiptasia, then focus on the smaller polyps to break their cycle. There is enough in the bottle to treat 200 aiptasia and an angled application needle to get the more awkward to reach ones.