I have a 46 gallon fish only tank with about 3-4 inches on sand and about 40lbs of rock. The sand and rock were once live, but I moved and took a few years off from running my aquarium. I have it going for about a year and all is pretty well, but my nitrates are starting to creep between 40-80. I've done four 10-15% water changes in the last 2 weeks, but the nitrates are still above 40. I've reduced the amount of food i've been feeding them. Is there any additive I can use or is there a way to make my sand live again to help out? I'm running a protein skimmer and a HOT magnum filter with a bio wheel. I only have four fish in the tank. Thank you!