Hello Thank goodness i found this place i have been reading thru this and have found some very interesting information but i was wondering does anyone out there use a digital tester and if so what do you recomend.???? being color blind i can't really use the test strips accurately.... also I just bought a new Intex sf15110 sand filter...... and i am having a hard time finding #20 sand for it is there any other sand i can use your helpwould be greatly appreciated