good eye beto, i had missed that completely. the one in the center is indeed just a shroom, but the one behind it to the right is an aptasia, not something a person is likely to list as one of the selling points of their tank. aptasia are a troublesome pest anemone that may sting your other coral. they are prolific and if left unchecked can easily take over a tank. i' either snag some peppermint shrimp, which are hit and miss, or try one of the commercially available aptasia killers. i like aptasia x, or you can make a kalk paste cheaper and arguably just as effective.