I have two twelve gallon nanos. One with a prizm and one without. The skimmer should reduce the nitrate levels, but I don't know if it is of real concern. I have seen quite a few tanks with out skimmers or refugiums that do just fine. I would strongly suggest not useing the prizm. It's a pain to constantly adjust and I have to take it apart to clean it every few months. I have heard and seen good things with the back pack. Both of my tanks have been running for a while and I realy can't tell a difference.