general hardness is the total amount of dissolved solids in your water. this and your pH will let you (and everyone else trying to help you) how hard or soft your water is. pH alone is not a good way to determine the hardness (or softness) of your water. the higher the gh, the harder your water
it could any number of diseases. as far as i can tell, sitting on the bottom is not normal for mollies. did you grab cycled media for your qtank? it could be your tank is cycling and your mollies arent feeling good due to this (though your general parameters look ok). what temp are you keeping them in?
you test for gh like you do any other parameter; there is a test kit available for gh. its usually sold separate. also, are you using a liquid test kit or test strips?
you test for gh like you do any other parameter; there is a test kit available for gh. its usually sold separate. also, are you using a liquid test kit or test strips?