Refugium Impact on pH (or am I interpreting this wrong?)

[Zach0918]

So I run a reef tank in my high school classroom. I haven't bothered too much with pH until this point but recently we started adding corals and studying water chemistry. When I first took a look an our weekly graph on fusion I was surprised to see how immediate the impact from students in the classroom was on our pH. My students come 7:10-7:20 each day and my classes end at noon every day. Almost as soon as my first class would start my pH would begin dropping, until noon when my last class ended. Usually the drop was about 0.2. At noon it would immediately begin climbing again. On the weekend, when no one was in the room, pH was relatively high, which made sense. All this seemed to make sense and was a great model of ocean acidification for the kids.

Last Thursday we spent some time optimizing our refugium light with our PAR meter, just really looking for max light output (for now). There has been a significant change in the previous pH change pattern. The swing during school days are not a as drastic and the minimum pH has increased pretty significantly. Is it possible that the increased light could affect the refugium efficency to this extent? Could the macro really be converting this much carbon dioxide? Or am I missing something here?

 

[IntrinsicReef]

It looks to me like a .1 bump from the refugium. That seems about right to me. The lack of people in the classroom looks like about .18 bump. This all tracks with my experiences

 

[Seansea]

Algae soaks up co2. Makes sense to me

 

[Randy Holmes-Farley Verified Community Expert]

It might also be pH calibration drift, but in general, refugia can raise the pH.