Thanks JDM My tank is a 15 gallon tank. Will be doing a 50 percent water change today and smaller water changes on a daily basis until I get the nitrite level down to 0. Yes, I am Prime so it does include eliminating ammonia. I just had another fish die on me so down to 6 =/. I wish I had done the filter swap the right way from the begining.. but oh well nothing I can do about it now except for this. How long do you think it will take to get the nitrite down to 0?