Was looking for this exact same Q and A. Hope someone chimes in.There is some great information here! I have an additional question. My ph just before my lights and co2 come on is 7.6. My ph just before my lights and co2 go off is 6.8. MY KH is 4. I currently do not have fish in my tank, but hope to get them soon. My question is, is it OK that my ph is fluctuating this much every day???