Take a look at this pic and tell me what you think. If you need a better pic I can try and get a better one. The rock in the pic came out of my biocube. I never had a problem with aptasia, but if you look to the leftt of that tuft of hair algae, I'm not sure if those are aptasia or small feather dusters. When they are brushed they recend back into the tubes, and the tubes are semi hard. I have one aptasia in my 30gal my pepermint shrimp havnt eaten yet, but when he is bothered, he recends all the way into the rock.