They do cause issues and tho it is sweet seeing little stars all over - if u are planning a reef long term in the end you will most likely not like these guys. It wouldnt keep me from buying the system but i would pull them out the best i ccould.I have seen them finish off zoas having probs that may have made it. There are many diff types it seems also as i have found at least 6 variations in the tank. I have also found one that messes with monti's (i will see if i can find the pic). I have even questioned on strain on sps - they eat off of problem areas with diff corals seeming to increase and make the problem worse.
Also it is a hit n miss on harliquins with these. Sometimes yes sometimes no but everytime not a suitable food source for them. I have had multiple and they are exactly what they are decorative and delicate. I have watched one of my male harliquins remove a 3" chocolate chip star from the glass and bring it back to his lady. He was the size of maybe a quarter - they ate on this for a good 5-7 days straight. So think of a diet consisting of only astera stars as one of us standing in super high winds eating only apples all day long.lol
Just some experience with them - mine and the wives fav specimens - and absolutely gorgeous. But they take a lot of time as far as live stock is concerned.