pH drop and ORP spike overnight

[rzimm33]

Hey,

Last night my system pH dropped to 7.47 which is very atypical. Inversely the ORP spiked to 245 which is also unusual. I know as pH goes down ORP goes up, so the relationship there makes sense.

I am just baffled as to what lead to this sudden drop in pH.

Most nights the lowest my pH goes is around 7.9. While the highest my ORP ever goes is around 230.

My system has maintained stability and not experience a swing in pH like this in over a year.

All other perimeters are as follows:

Alk 9
Ca 470
Mg 1345
Salinity 1.024
Temp 78
Phosphate 0.07
Nitrate 0.0 (even with adding and heavy feeding)

The only abnormal thing that occurred last night is we used a new cat litter which is located about 10 ft from the tank in a closet.

My skimmer utilizes outside air.

I’m wondering if anyone has a possible suggestion or explanation what could have possibly lead to this large drop in pH.

 

[rzimm33]

if it had only been the pH to show an abnormal reading, I would have thought faulty reading from probe. But since the ORP also showed a sudden change, it seems less likely to be a probe issue.