Hi - I am stumped by this PH question . ..
Background: I have 50 gallon, heavily planted tank with a heavy fish load. I am running T5s with plenty of light. There is a pressurized CO2 system with a solenoid and PH monitor. The solenoid is plugged into a power strip that alternates current from day to night. The lights and solenoid are plugged into the daytime side, and air pump on the night side. My canister filter and ciculation pump are on 24/7. It has been up and running beautifully for 1 year, the CO2 system for about 4 months. Everything is thriving. The PH would swing from 7.2 in the morning before the lights and solenoid come on after aerating all night, to 6.2 at the end of the light cycle.
Problem: For the past week I have noticed that the PH monitor has read 6.3 or 6.4 all the time - morning, noon, and night. This doesn't seem right or even possible to me. I checked and the solenoid is working properly in that if I force it to come on by changing the "alert" setting, it does come on. If the canister was out of C02, wouldn't the PH be high all the time, not low?
What might cause the low PH? I did a large water change last weekend but I use RODI water and condition it with a product to correct the PH . ..
Thanks in advance. If I didn't give enough info, just ask.