I own the Twinstar Shrimp . It was on sale at Garnelenhaus and decided to take the plunge and try it out. Overall, the shrimps don't seem to mind it, as they sometimes swim through the bubbles it creates. I'm not sure about the positive effect - although from my observations it seems to stop the production of most algae ( even though the Shrimp version is supposed to be more targeted at preventing shrimp diseases, not algae eradication ). I'm quite happy with it overall. Not sure if I would buy one for a future tank though, as the effects aren't really tangible.