About 2 months ago I changed the gravel in my freshwater tank to sand. I completely cleaned the tank before i put the sand in, but ever since I changed it, it has been cloudy. I like having the sand on the bottom and I got it from my local pet store and it has been in the tank for around a month. It is driving me crazy that my tank will not stay crystal clear. I even changed the cartridges in my filter and that is running fine so i have no idea what is going on. I've also done several full water changes. Will i have to change sand or just switch back to gravel? Help me!