My tank is 4 foot long, 1 foot wide and 20 inches tall, with water kept up to 4 inches from the top . I have a little over 1/4 inch of sand on the bottom, hiding places, plastic plants and an internal filter . The temp is 66 degrees F usually sometimes less . 3 axolotls have lived in this tank for 3 months and I had some fish in there before them for about a month . My readings have been ammonia .25 to .50 , nitrite 0, ph 7.6, nitrate 0 . I change 20 % of the water every day if not every other for sure and get rid of the poo when I see any . I would think by this time my ammonia would have dropped to 0 but no it hasn't . I was wondering if any one uses ammonia chips or ammonia filter inserts to remove ammonia ??? My 3 axolotls seem very happy but this tank is driving me a little bonkers . Thanks for any help . Dianna