hi just got a jebo 178 hang on skimmer for my 20 gallon i know it is not the greatest skimmer. just got it running and there is a air hose inlet that you can adjust the amount of air when it is totally closed it does not seem to do any skimming when you open it creates alot of tiny bubbles and alot of them ed up in the tank. the skimmer also becomes very loud does anyone have any clue how to use this thing the instructions are terrible please advise thanks