Hello all I'm new to this site and joined cause I'm seeking information that is apparently hard to find. Quick back story is I've been reading up on aquaponics for over a year and built my first system roughly 4 months ago. My fish tank is 100gallons and the water comes from city water but in South Dakota that is fairly clean water, my grow bed is 50gallons and uses a River Stone media about a foot deep. My system started off well with decent plant growth and very rare fish (Yellow Perch) deaths, the system is currently in my basement which maintains a constant air temp of around 64-70 degrees in the summer and uses 2 large 48" growlights.

Now that some of the spec's of my system are out there my problem is with a HIGH pH, now videos and other sites pretty much all explain how to make low pH systems higher but rarely the opposite. Before I built my system i tested my tap water which read 7.8 then with rocks in it which was basically the same and hoped it would lower itself to 7 or so over time. Now 4 months later my system has been running and my plants start off well then over time begin to yellow up or get brown which tells me Nutrient Lockout as a result of high pH. I've even bought a pH down solution for aquariums and over a week or so time emptied the bottle into the system and I haven't seen it budge. Now after thinking about it the area I live in is mountainous and has quite a few large Limestone deposits which could explain why water straight from the tap is already 7.6-7.8

I guess my question comes down to does anyone have suggestions on what to add to get my water level down and if anyone has suggestions for media that would be more pH neutral. I know Hydroton (clay pellets) is the best solution but I'm fairly sure my entire state doesn't sell it at all and to have 12 40L bags delivered is insanely expensive + $20-$30 a bag.

Any help or suggestions is highly appreciated, I'm really aiming to revamp my system before the heavy SD winters coming baring down in less then a month.