We are semi new to our 40,000 gallon pool. We originally had trouble with cloudy water. We continued treating it and now it's green! Our PH is right on target as is the rest of the chemicals. We have a sand filter that we just replaced the sand in and we are running the pump/filter day and night the last 48 hours. 20 hours ago we added an Algecide and super blue. Still green! What else could it be?? Is it possible we just aren't being patient enough? I've back washed the filter a few times. Help!