[karimwassef]

I monitor my pH and drip when it falls under 8.34 to maintain an Alk of 9. This loop is always running. I have massive aeration of fresh air so that keeps my measured pH and Alk directly correlated.

I determined the 8.34 experimentally. I changed the set point slightly and measured the resulting Alk. I recheck every month when I calibrate.

I use two probes to make sure I don't have runaways and other failsafes like salinity, etc....

I don't use a doser. I use a solenoid from my RODI reservoir to feed my kalk reactor which drips in the highest agitation region in the overflow / sump.

This has worked for about 5 years with great success except when I lost my outside air aeration for a week due to laziness (maintenance of the aerator). The pH and Alk got disconnected as the inside air CO2 levels were much much higher and more volatile. This caused an Alk spike and sps burn.

When running properly, I can maintain Alk constant 24/7.