Hi I have a 120 gallon with 5 smaller fish have a 40 gallon sump tank is 9 to 10 months old.All parameters check out at 0 ppm ammonia,nitrite,nitrate .My ph is 8.3 my phosphate read zero also on a API test kit.i can not get cheato to grow ether I run gfo,gac and filter sock change every 2 days...