Hi James - That is exactly what I'm worried about. Today I started adding dechlorinated tap water. Here is what I've been doing and what I plan to do:
Since the startup of this tank 5 months ago, my water changes have been daily at 50% with RO water and I have been adding back in minerals for plant growth 2 out of three days. Up until I added the 18 discus 2.5 weeks ago the pH has been 6.5. Since then the pH has fallen to 5.4. As of today I have stared adding dechlorinated tap water in the amount of 2 cups her feeding. This may not be enough, but I am starting here. My tap water is around 8.2 pH. What would you suggest at this point to avoid a pH crash?