Despite weekly water changes and fairly consistent water levels of 0 GH 0 KH 6.5 PH 0 N02 and 0 N03 my 60 Gal tank has decided to look like the picture below. I have not the foggiest idea what is going on. At first I thought it was tannins but the color is all wrong, so then I thought it was because I had gravel in the tank which I figured was keeping a lot of the poop trapped underneath it; so I switched it out with sand. It was an all day project, and when I was done I thought I'd gotten it right. A few days went by and It started coming back. I then thought it could be little pieces of my plants falling off and breaking down in the water causing it to be murky, so I took out all my plants, and did a 50% water change. After the sand resettled it looks like I didn't do anything at all! I'm assuming it's Algae and have left the light off for 4 days now, with no signs of clearing up. I'm left scratching my head because I don't see any algae on the glass or anything, and I've only got 6 fish in the tank, and they have been on a diet to eliminate the possibility that I was over feeding and didn't know it. I'm fresh out of guesses. I would LOVE any advice/ideas you can supply. I really want to see my fish 


