Large pH spikes with new sump light

Reflective · Dec 9, 2015

So I bought a stronger light to put over my sump, and I am wondering if the light is too strong since it makes my pH jump by .4 or more every time it goes on and off. With my tank lights on during the day, the pH stays around 8, at night with the sump light on it says around 8.4-8.5. Takes about 30 minutes for the pH to jump from one to the other.

Randy Holmes-Farley · Dec 10, 2015

Where are you measuring pH?

Is there much flow through the refugium?

So to clarify, when the light turns on, the pH drifts steadily up for 30 minutes? It does not mostly happen instantly?

Reflective · Dec 10, 2015

Now I feel silly. I have my probes in the refugium. Last night it climbed from 8.06 to 8.89. So I definitely thought everything was going to be dead. I got downstairs and still saw fish swimming so did a quick pH test from the display tank and it showed 8.2. Took out the pH probe and saw it covered with algae/slime on the end. Cleaned it off and stuck it back in and it says 8.2.
Not sure why that wasn't the 1st thing I checked... I blame pregnancy brain.

I'll definitely move my probes elsewhere as well.