Something that may be of use for those of you who want perfect water. I have been using Bio Chem-Zorb,Nitra-Zorb and Phos-Zorb for the last year now with great results. I just place the pouches inside my cannister power filter and forget it for around 10 weeks. (sometimes a bit longer)All my water readings are zero, with the exception of my Ph. All my fish are happy and healthy, what more could you want?