The tank is 144x48x48, sump is about 400 gallons.
I just got back from there and fixed the CO2.
It was pretty bad, they could not measure a rate due to the sensitivity at such high flow rates. Adding to that, poor pH probe calibration etc, now, after installing a viscosity flow meter(not cheap), we can easily measure mass flow volumes and trim the flows very precisely with a needle valve.
That+ good pH probes(new ones), + O2 enrichment, and monitoring set up, Neptune controller Pro 3 set up, things are looking up.
Regards,
Tom Barr