I have a 55 gal cant seem to keep ph above 6.5 now my hot water out the focet is 7.6 and the cold is 7.4 togather i get 7.3 but that only last about 2 days then im down to 6.5 my amonia is always 0 and so is my nitrate and nitrite,i have a fluval 404 and a 204 on it.