In The Tank

I currently mix half raw well water with half RO water for use in my aquarium. This involves bypassing the water softener. The softerner's bypass valve is very awkward to use and, being plastic, it scares us. I can get water from a spigot between the well and the softener but it is really turbulent. If I let a glass of water sit, I get a good 1/8" of sediment. I want to filter the water directly from the well. How many microns should I shoot for? Oh, and the pressure at the well is about 60 psi, if that matters. Thanks.