I have a 55 gallon reef tank. My Nitrates are at 60 and I cannot get them lower then 40. I have done numerous water changes and Istill cannot get them lower. I only have 4 fish and some inverts. All of my other water parameters are perfect. I do not have a protein skimmer. I know I need one and I am saving for one. I should be able to get me Nitrates lower then 40 without one though. Please let me know what else I can do to get them down. Thansk