Best Time to Take ph readings

Hi All,
I tested my ph just as the lights came on in the tank. The reading was 7.9 which is quite unusual as the normal ph .8.4

I took the reading again about an hour later and sure enough it was 8.4

Normal and Current readings for the tank are:
ph 8.4
Calcium 430 ppm
Alkalinity 10.4 dkh
Mg 1300

 

That's quite normal as pH usually drops at night and rises during the daytime.

The pH will also change as fish are added or removed and even as water is added (or changed).

The important thing is to take your readings at the same time of the day with each testing.

 

I always check mine in the afternoon. Not saying thats right, but that's the time for me....

 

When you test your pH, you MUST do the testing consistently at the same time or you will have varying results as you found out!!!!
If you normally test during the day, you must always test during the day or vice versa at night time. The reason for this is that pH will shift from daytime to nightime due to the amount of dissolved oxygen in your water. The highest pH reading you will encounter will be during the day with your lights on due to photosynthesis. The lowest readings will be encountered at night as photosynthesis has stopped due to the lights being turned off. You can helpt to decrease this from happening by running reverse daylight lighting in a sump or refugium housing caulerpa or other forms of macroalgae!!!
Be aware of your alkalinity levels as well as a higher alkalinity level will help your water to resist changes in pH(buffering capacity). Less pH swings due to higher alkalinity will create a more stable environment for corals especially.
Over time due to livestock respiration and metabolism of bacteria and animals, acids are produced such as uric, organic, humic acids and carbon dioxide, all which will cause your pH to decrease in due time, so the addition of kalkwasser will help to raise and maintain a stable and higher pH since the pH of kalkwasser is around 12!
Hope this helps
It is advantageous to maintain a balance of buffering and alkalinity to conteract the pH shift tendencies!

 

best time is after your lights have been on for 1-2hour+
TRy a refguim and that should stablize your PH a bit more

 

Just testing a marine systems P.H with a Liquid PH test kits is next to worthless as is P.H anyways you just test for Carbonate levels then the P.H will take care of itself A P.H monitor is the best way ..

 

Thanks everyone for their knowledge and experience. I had a feeling that ph flucuated from night to day. Also, I have maintained fairly balanced Alk/Ca parameters, so what you are saying Tangster makes a lot of sense..Everything is flourishing in the tank....8)

 

Yup! Tangster's right. I was driving myself crazy til I got a Ph probe.

 

I was always told to check your ph right after your main lights turn off. That will be the best reading.

 

I have a question.....what would be the normal pH at night if the pH during the day is 8.3?