That's a macro algae - good algae to have in a sump. If you don't have a sump and don't want it in your tank, pluck it and offer it on Offer Up, Craigslist, or your local group here on Reef2Reef or Facebook.How do you treat that, because that’s exactly what it looks like? Introduce a snail? I’m new at reefing. Only been doing this 5 months now.