I have 2 Aqua Medic skimmers on my 8 foot all reef tank. Over the years I have had nothing but problems with poor skimmers and so I purchased these so called 'good' skimmers. They are 'hang-on' skimmers as I don't use a sump. The problem is that they seem to stop working on a regular basis and need the power heads, which sit in a pump box at the end of each side of the tank to be adjusted i.e. moved around until one hears the air being sucked through the pipe again. They aren't blocked and usually where moved a little they work again. Any suggestions would be appreciated or even a better hang-on skimmer!