if your talking about the marineland marine series skimmer they are alright. there are better out there for the MSRP of $200 but its doable. way better than seaclones, prizms and that level of skimmer. not quite up with octopus, vertex, aquaeuros which can be had for the same money. the larger model is not competitive with skimmers in its price range at all. $300 buys pretty good skimmers these days. if your talking seaclones the 100 is satisfactory for 30g or smaller tanks but I wouldn't but it on anything larger and its kind of noisy. many people say they cant get them to work well but I'm not one of them. mine worked all the time and pretty well (I have pics to prove it). its still an entry level skimmer. you wouldn't put it on an SPS or low nutrient tank. If your talking visi-jet, junk! save your $60.