Proper Ph level is 8.1-8.4. You should also be checking alkalinity. 'Alkalinity' is different than Ph (it's not how alkaline the water is). It's a measure of the 'buffering' capability of the water, which is what maintains a healthy Ph. I'm a newbie, but I check alkalinity (and calcium as well) and have generally been able to maintain proper water parameters with weekly 10% water changes plus topping off with a re-mineralizer additive, such as AragaMIGHT, which adds back calcium, buffers and trace elements. The only exception was a brief bout when our alkalinity and calcium dropped (probably due to coralline algae and coral growth zapping the calcium supply temporarily).