PH dips low at night?

[liusteven]

Randy,

Can you tell me why my Ph dips from 8.4 - 7.9 at night.. only the lights are out but the PH are all on.. also the sump light is on 24/7... Could it be the magnesium.. last I checked I was at 1300..

Thanks


Steve

[Randy Holmes-Farley]

Magnesium won't impact pH in that fashion.

During the day, photosynthesis consumes CO2 and drives up the pH. At night that process stops, and CO2 rises, both from respiration from tank organisms, but also sometimes from the air.

So the daily pH swing is normal, and varies from about 0.1 pH unit up to values like yours.

To minimize the pH swing, more aeration helps. Complete aeration will eliminate the swing. Also, putting a refugium on a reverse lighting cycle can help, as can timing the addition of high pH supplements, like limewater. Higher alkallinity also reduces the pH swing.

[liusteven]

Randy,

Thanks for the feedback... My PH has been the same and my PH swing was normal like from 8.3 (day) dips to 8.0 but these days it dips as low as 7.7?

I do limewater topoff at night to minimize the drop but it still is not working well.. I will check my dkh today...

Off the subject:

Do you know why my PH can go up to 8.43 (after 9 hours of lights)?


Thanks

Steve

[Randy Holmes-Farley]

Do you know why my PH can go up to 8.43 (after 9 hours of lights)?


Why? Because photosynthesizing organisms are using up the available CO2.

Indoor CO2 levels can change through the seasons and can drive aquarium pH up or down. If your house is closed up for the air conditioning season, then CO2 may be higher now, so the pH drops lower.

This article explains the indoor CO2 issues:

Indoor CO2 Problems
http://www.advancedaquarist.com/issues/apr2002/short.htm

[liusteven]

Ahh... thanks

[Randy Holmes-Farley]

You're welcome.

Happy reefing. :)