I have a 400l 120x70x50 Amazonian tank which has been running for around six months. It is heavily planted with co2 injection. Currently there are only 19 fish in there, 12 Black Phantoms, 3 Bristlenoses, 3 Peppered Corys & 1 Clown Loach. PH = 6.6, KH 4-5 Amonia, nitrate & Nitrite almost nil...