Very small nems. I have a colony of zoas I had purchased and these were spread amongst the polyps, I just thought they were an interesting looking paly's. They seem to be bothering the polyps and I liked how they looked so I cut around the polyps and took them out. They came out so easy, once I used razor on zoas they just fell out. I super glued them to a plug and put them back in my system. Looked at them later and noticed a few polyps gone, just thought the current had got them. Then I noticed how all of the others had moved around on the plug. One was even on the eggcrate. I do not know if they would be like an aptasia and need to kill or what. They are cool looking. Size reference: the disk is 1 1/2" in diameter. The redish spots on disk are the superglued areas.