Skimmer discharge CO2 enough to react with media?

[siggy]

I have a question with elevated co2 and skimmer discharge. I cleaned out the sump after a year, the fudge section is following the skimmer and the dead frag skeletons turned to mush when handling.
Is that due to CO2 in the discharge , kalk in the top off , all or nature of things.
Also Would there be a benefit ( CO2 -PH) to installing a media chamber on skimmer discharge as a poor man's Cal reactor. what would the theoretical result be if any.

 

[Randy Holmes-Farley Verified Community Expert]

The pH coming out of a skimmer should not be lower (more CO2) than the tank water itself unless the tank water is already high in pH (low CO2). In such a case, the skimmer won't drive it low enough to dissolve aragonite.

What is the tank pH, typically, day and night?

The system may just be very low in pH, in which case skeletons can very slowly dissolve.