pH dropped after vacuuming sandbed

[Tbg299]

On Saturday, I did a 15% water change, and vacuumed cyano off my sand bed. I probably stirred it up more than I should have. My sandbed is not that deep; the deepest parts are 2". However I noticed afterwards on my Apex probe that pH dropped from 8.2 to 8.0. Is this because of the hydrogen and sulfur in the sandbed?

 

[KrisReef]

Could be. Could be from the new water addition?
I hate to speculate but somebody has to.

 

[dk2nt9]

Check alkalinity too, if it was used, it's time to add more.

 

[HuduVudu]

Likely an organic release. This happens when stuff that was breaking down anaerobically gets exposed to a lot of oxygen. This causes a nitrogen cycle spike which "creates" acidity. This will drop your PH and Alk.