I have 2 pressure tanks, 1 coming out of well, the other out of holding tank that goes into the house. I can control the water coming off the well into the tank if I run the well water in the tank on very low pressure the water will stay clear for hours, but if I run the well on high pressure then the water gets muddy/sandy within min. why??

You would have to call a well guy to be sure but it sounds like the water table dropped and the well's silting up. If you have a jet pump, (see image) then at low pressure you aren't roiling up the water but at high pressure you're agitating the water and disturbing the silt so it gets sucked up. Like I said, Get a well guy in to check the water table and to give you a estimate on pulling the pump and digging the well deeper. Good luck, Tom

You have a low yield well and you are over pumping it. Over pumping the well is the #1 cause of well failure. For a good explanation of why this is see http://www.wellmanager.com/wellmanager-environment.htm