pH plummeting when lights come on?

[shanepike]

Ok, so I have noticed the last few days that when my blue lights come on at 9:00, my pH plummets. Today, for instance, it went from 8.1 at 9:00 to 7.97 at 9:30. The fuge light is not</em> going off at that time. The only thing that's changing is the blue lights coming on. (They come on at 30% brightness, for what it's worth.) It's entirely possible that it has always done this; I'm not sure that I just haven't noticed before (though I would think I would have).

Any thoughts on what could be a likely cause?

Oh, and I just remembered that the canopy exhaust fan cuts on at the same time. The temp only dropped 0.2 degrees, but maybe a sudden increase in evaporation rate has something to do with it?

 

[y-not]

I'm sure others will correct me if I'm wrong here but I'm not so sure that 4 one thousands of a point constitutes a "Plummet".

Mine routinely varies from 7.85 to 8.09 within a 24 hour period.

Does anything in your tank appear to be suffering?
Are all the other water parameters good?

If so, quit losing sleep over a .04 swing in PH.

 

[eric b]

I would not consider that plummeting either and I would not go chasing PH numbers if all your other CA/ALK/MG are in the proper ranges.

 

[y-not]

Y-Not;883204 wrote: I'm sure others will correct me if I'm wrong here but I'm not so sure that 4 one thousands of a point constitutes a "Plummet".

Mine routinely varies from 7.85 to 8.09 within a 24 hour period.

Does anything in your tank appear to be suffering?
Are all the other water parameters good?

If so, quit losing sleep over a .04 swing in PH.

My bad...
It appears that I'm loosing my math skills.

Your Ph drop is 0.13 of a point.
Still nothing to loose sleep over.

 

[shanepike]

I wouldn't be concerned if that drop was over the course of a day, but a) over just 30 minutes, b) when it's been consistent the entire rest of the day and c) at exactly the same time the past few days.

 

[shanepike]

Maybe "concerned" isn't the best word, but I definitely want to understand what would cause this:

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[eric b]

Could have been some kinda of miss reading maybe with the apex maybe flow changed for that time around the probe? How old is the probe? I have seen 2 probes both calibrated the same time and placed one in the sump the other in the tank and both read differently on the same apex. I would just keep an eye on it to see if it happens again!

 

[shanepike]

I definitely considered that it might be a problem with Apex and/or probe, but it has been perfectly consistent for at least the last five days (as far back as I can go right now):

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[shanepike]

Alright, so this morning I manually turned on the blues & fan 5 minutes early. PH plummeted as soon as I did rather than waiting until 9. I suspect it's something to do with the fan, so tomorrow I will turn on only</em> the blues and see what happens.

 

[y-not]

ShanePike;883412 wrote: Alright, so this morning I manually turned on the blues & fan 5 minutes early. PH plummeted as soon as I did rather than waiting until 9. I suspect it's something to do with the fan, so tomorrow I will turn on only</em> the blues and see what happens.

You may well be onto something here.
I've setup a number of computer networks in the past and electromagnetic interference is a mystical beast.

Check that the probe cable is not running inline with any other cable. Power cable, other probe cables, etc...

There's a note in the Apex manual about running them some distance apart or at 90 degrees from each other. Of course, that's not a quote but it goes something along those lines.

My salinity measurements were all over the board until I routed the salinity probe separate from everything else.

This could be the key to the sudden, predictable drop in PH.

 

[shanepike]

Alright, mystery solved ... kind of.

This morning I opened my canopy at 8:20. Nothing else changed. I simply opened the canopy to let it vent. Immediately</em> pH began to drop. The lights came on at 9:00 as usual, but the pH drop had already been happening for 40 minutes.

So what is it about venting the canopy that causes pH to drop so precipitously? I can imagine that the evaporation increases substantially, but would evaporation cause a pH drop like that?