Dark Blue/Black Coral

[Tankster]

i had a sponge like that, if too much just grab a handful and pull it out. I wouldn't worry too much about it though.

[ReefTech]

i had a sponge like that, if too much just grab a handful and pull it out.

+1 on it being a sponge. I had the same thing growing in my sump before I drained it to move it into my basement. It was actually in my refugium but never spread anywhere else so I was never concerned with it. Just as Tankster mentioned you can just remove pieces of it by pulling them out with your hands. Your gonna need to keep an eye on it cause the one I had just spread everywhere with no sign of stopping so it may just continue to spread everywhere in your tank if you don't keep trimming the branches back. Not sure what kind of water parameters are needed to get this sponge to form and grow cause ever since I drained my sump, moved it, then refilled it and started running it I don't see any signs of it growing anywhere anymore.