Good pointy about the water.. Tap water will work but only if the PPM is not to high.. If the parts per milion is over 100 before adding ferts you should consider getting something to to make your water better.. if your tap waters parts per million is 200+ and you are growing hydro, forget it will kill the plants in week 3 of veg. very sad..

the mixture ratio you want to use in aero or hydro system using GH nuts is..
3micro, 1grow, .5 bloom - druing veg period..... NOTICE BLOOM is "POINT 5"


good luck : )

SMB