Daily ph swings

[frenchie01]

I seem to have 2 ph swings in a 24hr period, is this right?

My ph starts to go up when the lights are at their strongest, when the t5s come on at 12pm, and then when they go off and the leds start ramping down the ph goes down. Until all the lights are off and the ph creeps up again, between 8-9pm, and then starts it’s descent again at around 7am. The ph stays at its peak for around 2-3hrs.
I have an algae reactor lit 24hrs and thought this would keep my ph pretty stable.
The swings are around 0.25 each time

 

[Lasse]

This was very interesting - can you put up a graph

Is there any possibility for you to measure PO4 (or P) just before the pH going down and just before it goes up (both cycles) What’s your NO3 levels and are your test set able to show small changes.

Sincerely Lasse

 

[frenchie01]

It’s difficult to test just before the swings as I’m at work, but my last test were no3 2-5 (salifert) and po4 0.06 (elos). Ph is tested via apex and was last calibrated 3-4 weeks ago

 

[frenchie01]

Also I understand the rise at peak lights to be because the algae within the corals will be photosynthesising and taking up co2 but why the fall and rise again when the lights are off.
I thought the algae reactor being on 24hrs would prevent this

 

[Randy Holmes-Farley Verified Community Expert]

The other main things that impact tank pH are:

1. photosynthesis and respiration in the tank consuming and producing CO2. Goes with light cycle.
2. The presence of people, pets, and cooking with gas stoves in the vicinity of the tank or sump that increase the local CO2 levels.
3. Addition of organic carbon lowers pH in the hours after dosing (and immediately, if it is vinegar).
4. Addition of alkalinity additives that may raise pH.
5. Electrical interference from lights or other electrical devices can impact some pH measurement scenarios and devices.

 

[rkpetersen]

That pH variation pattern seems very strange. The rise after lights out in particular is hard to explain unless it involves one or more of the factors 2-5 that RHF mentions.

Here's what my pH cycles looks like:

Keeping an algae reactor on 24/7 might keep the average pH value higher, but it won't stop the swings that occur due to respiration and photosynthesis inside the tank itself.

 

[frenchie01]

The other main things that impact tank pH are:

1. photosynthesis and respiration in the tank consuming and producing CO2. Goes with light cycle.
2. The presence of people, pets, and cooking with gas stoves in the vicinity of the tank or sump that increase the local CO2 levels.
3. Addition of organic carbon lowers pH in the hours after dosing (and immediately, if it is vinegar).
4. Addition of alkalinity additives that may raise pH.
5. Electrical interference from lights or other electrical devices can impact some pH measurement scenarios and devices.

1. That would explain the daytime swings but why the night time swing?
2. It even happens without people in the house, maybe a not as big a swing
3. I don’t add any of these
4. I switched my calcium reactor off to a while and it still happened.
5. This happens with my conductivity probe when my t5s go on and off but it’s an immediate jump, my ph rise/fall is gradually

 

[Lasse]

The thing coming up in my mind is that you are limited of one of the main nutrients. The production off inorganic P and N goes on the whole time. Mainly by bacteria. If your photosynthesis consume all (or all of one) nutrients during your main illumination (the DT) – the photosynthesis will go down in intensity and there will be lower photosynthesis by the macro in spite of the fact that the light is on 7/24. After some hours – your bacteria have produce so much inorganic P or N so the photosynthesis can rise for a while again. But I´m not sure on this


Sincerely Lasse

 

[frenchie01]

The thing coming up in my mind is that you are limited of one of the main nutrients. The production off inorganic P and N goes on the whole time. Mainly by bacteria. If your photosynthesis consume all (or all of one) nutrients during your main illumination (the DT) – the photosynthesis will go down in intensity and there will be lower photosynthesis by the macro in spite of the fact that the light is on 7/24. After some hours – your bacteria have produce so much inorganic P or N so the photosynthesis can rise for a while again. But I´m not sure on this


Sincerely Lasse

So would it be best to reverse light my algae reactor or would this make no difference?
Or should I feed more to raise nutrients?

 

[Lasse]

I´m not sure at all on this - its only a theory. You are low in pH - you use a calcium reactor. Be sure to rule out that it not depends on how many persons you are and if they are sleeping or awake. On my pH I can se when my grandchildren awake in the morning if they visiting us for a sleep over

Sincerely Lasse

 

[Larry L]

I have an algae reactor lit 24hrs and thought this would keep my ph pretty stable.

I think running the reactor 24/7 might raise the pH at times when pH is low (by consuming CO2), but not as much when the pH is already high. So it might reduce the magnitude of the swing, but won't get rid of it. If you wanted to try to level out the swings, you'd probably have to run it off-cycle from the lights, but that might be counterproductive by leveling them out to a lower average than you have now.

Personally I think the low points are more of a problem than the swings, so I'd check if any dosing or anything is going on at that time that would lower the pH, and move it to a time when the pH is normally higher.

 

[frenchie01]

Looking at the swing times, the day time one coincides with the lights ramping up and down and then the night swing coincides with bedtime

 

[frenchie01]

I should also mention that I have an airline to outside and connected to a co2 scrubber that is connected to my skimmer

 

[Randy Holmes-Farley Verified Community Expert]

Looking at the swing times, the day time one coincides with the lights ramping up and down and then the night swing coincides with bedtime

Where do you sleep in relation to the tank? Near? Far?

Your presence in the room alters the local CO2 level.

Do other room lights change?