Sand is about 2" deep, its stirred once a week with the siphon. Test kit isn't even 6 months old. Fish seem fine, other than my Oscar who was HLLE, which he had when I rescued him from a overstocked and neglected 60G tank. I've also restricted feedings to every second day and to less food. I guess ill keep doing 25%-30% daily water changes. If I don't notice something in a week, Ill try a new test kit. Also I agree, sometimes the API kits are very hard to read, it looks like either 80 or 160ppm, depending on the lighting, very frustrating.