You figured it out! I quit commenting because your readings were over my head. Congratulations to you and congratulations to the smart people on simply who figured it out.
It might be a good idea to add some of the rock or some crushed coral to your aging barrel, but I don't know for sure because I've never had water like yours. Luckily, you're in good hands here on Simply.
Mama Bear
The reasoning behind leaving the rock in place is because the discus I'm getting are coming from the higher PH range. And wouldn't putting the same rock in my aged water barrel keep the PH where my tank PH is?
I've talked with the people at Chicago Discus and they recommended the same, take out the rock. So they are coming out of the tank. It's just irritating when you buy something based upon a recommendation of the store employees and they are wrong.
I will be testing my water after they are out and hopefully I get some matching readings.
Yes indeed. My tank finally has its first reading, .25 ammonia.