I have had my tank setup for 6 yrs now and everything has been pretty good. I recently added a 150 gl sump and 30 gl refugium into my system both of which are in the basement. Since doing this I have not been able to get my nitrates below 25 ppm. I have tried everything I can think of to lower nitrates, but they keep rising steadily. The big question I have is, does my cats litter boxes close proximity to my sump have anything to do with my rising nitrates? It is the only thing I can think is causing this problem. Any help would be appreciated.