ken shaffer: "ph 7 (apparently the co2 has effectively lowered the ph of my tap water from 8) GH 80 KH 60 Phosphate above 5.0 NO2 no trace NO3 no trace Ca 140 Fe no trace. lighting is approx 2.4 watts/gal co2 1 bubble/ sec." Hello Ken, I will let the experts analyse your values. But the GH and Ca values looks strange to me. GH = Ca + Mg. But your Ca values > GH. BC (Singapore)