Emmet
New Member
Can you double check the pH? Its a logarithmic scale so the difference between yesterday's 6.5 and today's 7.6 .is pretty big, although your first post did say between 7 and 7.5. As a control it is worth putting some tap water into a glass and testing it for pH after 12-24 hours. If its the API master kit test with both the pH and the pH high test. One of those will be off the scale - the other one is the one you need to use in future.
An interesting (but not essential) test would be to compare the NO3 in your tap water immediately before the water change. No need to wait as that won't change once it is out of the tap. This may provide a clue as to how far along your cycle is.
I'll begin now.