There has been a lot of discussions recently about raising PH via feeding your skimmers air intake from outside the property. My tank is approximately 4 meters from my living room outside wall and this is my plan to use the air from outside. I have just ordered a 5m length of white silicone hose with a 10mm internal diameter. You can buy smaller internal diameter but as the air intake of my Nyos 160 has an outside diameter of 10mm I wanted to use the maximum hose diameter that would fit on it (8mm fits tightly but I can use 10mm) I don't want pollen and dust etc getting into the pipe so I ordered 2 inline petrol filters (one will be a spare) to filter them out. I will fashion something with a more course netting to prevent insects getting into the end of the pipe (ideas welcome). The hose will be fed through the corner of the living room window frame. I hope the air filters won't put too much restriction on the air drawn into the skimmer but I think it will be fine, if not I can always use a coarser one with internal nylon netting type filter. Watch this space. The 5m x 10mm silicon hose. 10mm Petrol filter I am going to use as an air filter.