I have a 36 inch on a 90 reef . I really like it, just make sure to put enough pump on it and you will have a nice milky white column and a stable foam head. I have owned quite a few skimmers (top fathom, deltec 850, turbofloater, PM bullet 3, and a few diy skimmers. Each has its plus's and minus's. The Lifereef venturi has very consistant output, low maintaince, (dont pay extra for flanges-its not like a beckett which needs constant cleaning/maintance). I have not see the 24 inch model in action but my guess is it would do pretty well on a 125.