yea that is aptasia. I have about 10 total in the aquarium. They are a little bothersome but they dont spread too rapidly in my tank so I don't worry about them. My tank is basically maintenance free. I add water and change about 5 gallons every 2-3 mos. I feed strictly pellet food (spectrum) and add B-ionic 2 part buffer every ummm....whenever I think about it, which is about 2 times per week. I am a little ashamed to say the nitrates are 80+ ppm.... , but the inhabitants have been going strong with my malicious maintenance efforts for many years now.......I just recently tested the water...And to my suprise NITRATES. I may start doing more substantial water changes but I am happy with the tank and the way it looks so I may not do anything..... :lol: