I have a 10 gallon tank with 3 guppies, 2 black mollies and a pleco..I do weekly test on the water...I checked it today and the Nirates are WAY up!! the Nirites are normal. My water hardness is soft to hard, my ph is alkaline, but not way high..What should I do about the high Nirate? I done a water change today...Any help would be greatly appreciated!!! Also my male molly has a white film over one eye, and at times he hides, but comes out to eat..What would be good to use to treat this?? I also have a 1/2 tsp of aquaruim salt in the tank, will that hurt the pleco?