PH Drop After Adding Sand and Rock

[Yellow Eyes]

Saturday and Sunday I did a leak test on my new 20g set up with fresh Ro/DI water, I added salt monday and got my salinity to 35ppt, with a PH of 8.3. On Tuesday I drained my tank and added my dry rock and aragonite sand. The water got cloudy as I expected it too, no big deal. What I noticed though is that my Ph dropped (as read by my Neptune Apex) to 7.9. (Attached are pictures from the graphs). Currently it is still cloudy (I stirred it up a little because it got everywhere, not sure how it got so cloudy in the first place but I'm not too worried about it, it will settle).

Could this be something wrong with the measurement because of the silt in the water? Is this normal? It is started to trend back up.

 

[acabgd]

You shouldn't really worry about pH in a marine tank. Alkalinity is the important parameter.

 

[disc1]

You certainly shouldn't be concerned with pH at this point. Expect it to be low all through your cycle. The reason it dropped is because it came to equilibrium with the co2 in the air in your house.