ok i am having reading of about 5 to 10 ppm with nitrate and all other reading are at zero. either i have a bad test or something is wrong. i have three bio wheels, skimmer, 20 lbs live sand, 18 pounds of LR and its a 30 gallon tank. so i am just wondering where the nitrates are coming from since everything else is zero and my corals and shrimp looking find and not stressed so if any has any ideas on this let me in on some info.