My system is medium sized – 2 IBC totes as fish tanks, 2 55 gallon drums as clarifier and demineralizer for each tote. My raft bed is 20 feet long, 6 feet wide, and roughly a foot deep. I recently added water to my system and tested it. pH is ~8.4! I know this is higher than desired. All our water comes from a well, and this is likely entirely the cause.
Do I need to drive my pH down in order to allow the plants/bacteria/fish to live/grow in it? I already used a gallon of pH down and it hasn’t really changed anything (pH is still 8.4).
Your best bet is either to buy a RO system or use acid to bring down the pH on your top up water. Or collect rainwater but there are some challenges there as well(what is roofing made of and what might it leak into the water). How many gallons of water is in your entire system? What is in the pH down? There are some items used for bring pH down that you wouldn't want to add into your system in large quantities.
What is the pH of the water coming from the well before you add it to the system?