I've given this skimmer the old tryout now for 18 days. It's a poorly built device that doesn't do much more than fill your tank with micro-bubbles and foamy water. I have tried it up in the water and down. I have tried every air setting as well. Oh well a 160 buck big mistake. I believe I'll call it a failed costly experiment. I also believe that if you have a budget tank as I do that it's much cheaper to just control your bio-load the old fashioned way. If you have a sump then a real skimmer might be right for you. Don't waste your money.