Not sure what happened with my profile but it deleted my user profile and my original posts. But here is an update. I was on vacation over the last week so before I left I baked and crumbled almost a dozen egg shells and put them in very thin mens dress socks (like nylons). I put them under the water flow into the grow beds about 2 inches deep in the media. After 8 days I checked pH this morning and system is still at 4.0 still have eggshells left in the bags too. No idea what to do next. I have about a 1-1 ratio GB to FT, hydroton media, I am using yellow perch, I am not using a bio filter. I have changed 1/3 of the water out three times, and even drained the GB to waste and hosed them out to rinse thinking maybe they were anaerobic and creating low pH. I also have no carbonate hardness. havent lost anymore fish for the last week however. Test results are good and were done in a certified lab. I googled the black stock tanks that I have to see if anyone was complaining about low pH with them but didnt find anything. I have been filling the system with water from my pond ran through a sand filter. It has a pH about 7.8 and decent carbonate hardness. I have not measured ammonia or nitrates yet but will try to this week. Any