WYSIWYG Thick Well Seeded Halimedia, firmly attached to the rock chunk it is on as it grew in. While we lack the horticultural expertise to identify the exact species of Halimedia we know that it came from Indonesia, and that it has enormous blades compared to the more traditionally seen Caribbean Halimedia. There are some zoanthids still present on the rock, we have not seen then open in some time as the halimeda has been out competing them.
Several black colonial tunicates have grown on the undersides of the rock as well. This is a species that we have had popping up in our tanks for some time and have never encountered a situation where this creature has had a negative affect on a coral or any other tank inhabitant. They’re fascinating to watch!