Alkalinity rising quickly

[Randy Holmes-Farley Verified Community Expert]

No there was a good period around October-March where the tank was stable. Just over the past few weeks the alk has been raising just this week alk has gone up more then normal

Not sure why the rock and/or sand would dissolve more now, but maybe previously, nitrate accumulation was masking the rise.

I'd feed more to bring up N and P, and do water changes with a very low alk mix, made with the sodium bisulfate or muriatic acid.