Actually, there are some good biological reasons for utilizing aiptasia in a fuge- one is nutrient control, but algae also does that well with less risk of becoming a plague (but they don't remove suspended particles like aips do). The second relates to some experiments I've been running for about 6 months now. Having a good population of them is also effective in controlling and clearing ectoparasites- Amyloodinium and Cryptocaryon were tested. They actually have a very potent sting but their nematocysts are too flimsy to penetrate (most) human skin so we don't feel it, but the parasites sure do. They can be useful, but definitely plan a way to keep them contained.