Daily pH cyclic drift.

[pswag115]

Since we started full time pH monitoring I've noticed a daily swing from 7.91(7ish am) to 8.18 (7ish pm), this is in a Reef setup 80g AIO. All substrate and rock is live harvested from the Gulf near Tampa, tank is 3 months old. Only soft corals, 2 Clowns, some snails & hermits, Fire Scallop, and a urchin.

Is this a normal and if so is this in an acceptable range.

Measurments made with a Hydros probe and controller.

Thanks

 

[Randy Holmes-Farley Verified Community Expert]

Yes, a daily pH swing is normal and expected.

Photosynthesis when lit consumes CO2, raising pH.

Respiration by all organisms produces CO2 24/7, lowering pH.

The combination of these processes and aeration results in a swing in CO2 which causes a swing in pH.

 

[pswag115]

Yes, a daily pH swing is normal and expected.

Photosynthesis when lit consumes CO2, raising pH.

Respiration by all organisms produces CO2 24/7, lowering pH.

The combination of these processes and aeration results in a swing in CO2 which causes a swing in pH.

Thanks! I was just worried about the degree of swing.

Will relax a bit and monitor for changing swing values.

 

[Euphylliaphyle]

My 36 gallon had the same range. I attempted to level that out by adding an air venturi with airflow governed by a solenoid on a timer so it comes on while the lights are off. Crucially, I ran a tube from outside my house, through a jar full of carbon, to the airator. It boosted my overnight pH by a couple of points and now runs nearly identical to daytime readings.
Many people add a refugium with lights on/off opposite tank lighting. I don't have a sump, so that was not a good option for me.
All that said, I think you are fine with the range you have. I was just looking for better stability. TBH, my animals haven't shown any difference yet. Having a new tank, everything is still unsettled. YMMV.

 

[pswag115]

I do have an air stone in sump area, I could change it to only run night. Also have the compartment setup for running light at night in one of the sump compartments. I haven’t set it up or used it yet.

A lot to look into, thanks.

 

[Randy Holmes-Farley Verified Community Expert]

There’s no clear advantage to decreasing the swing. Aeration with inside air may actually lower pH overall, which is not a plus.

 

[Euphylliaphyle]

There’s no clear advantage to decreasing the swing. Aeration with inside air may actually lower pH overall, which is not a plus.

Randy, any insight into day/night pH swings out on the natural reefs? I would not expect much due to volume of water changeover. I would think that any photosynthetic effect would be quickly diluted and washed away.

 

[Randy Holmes-Farley Verified Community Expert]

Randy, any insight into day/night pH swings out on the natural reefs? I would not expect much due to volume of water changeover. I would think that any photosynthetic effect would be quickly diluted and washed away.

There is some variation, and especially in lagoons. I do not have the numbers handy.

 

[Euphylliaphyle]

There is some variation, and especially in lagoons. I do not have the numbers handy.

Makes sense, thank you.

 

[Lasse]

Randy, any insight into day/night pH swings out on the natural reefs? I would not expect much due to volume of water changeover. I would think that any photosynthetic effect would be quickly diluted and washed away.

There is some variation, and especially in lagoons. I do not have the numbers handy.

There has been a lot of reports according to this caused by the ongoing Ocean acidification. Here is one example and here is another. There is many more but it seems that there can be daily pH variation between 0.1 - 0.4 pH units at natural reefs. Here is an aquarium related thread also

Sincerely Lasse

 

[JulesH]

Ocean acidification sounds way more scary than becoming less base.

 

[Lasse]

becoming less base

This is just the definition of acidification and acidification is the scientific name of this process that happens today because of the higher CO2 pressure in the atmosphere. Is the same process you se in your own aquarium when you are more people in the aquarium room than usally or when you of temperature reasons not can have the windows open.

Other try to use another type of words in a political way in order not to call a spade a spade.

Sincerely Lasse

 

[Euphylliaphyle]

There has been a lot of reports according to this caused by the ongoing Ocean acidification. Here is one example and here is another. There is many more but it seems that there can be daily pH variation between 0.1 - 0.4 pH units at natural reefs. Here is an aquarium related thread also

Sincerely Lasse

Thank you, Lasse!
This graph from your first link above answers my question perfectly:

In it, we can see a sawtooth pattern of daily pH swings similar to those seen in home aquaria, including that of the OP @pswag115 posted at the top.
This seems to reinforce Randy's assertion from above:

There’s no clear advantage to decreasing the swing.

 

[Lasse]

Thank you, Lasse!
This graph from your first link above answers my question perfectly:

In it, we can see a sawtooth pattern of daily pH swings similar to those seen in home aquaria, including that of the OP @pswag115 posted at the top.
This seems to reinforce Randy's assertion from above:

You may find this interesting too

Sincerely Lasse

 

[Euphylliaphyle]

You may find this interesting too

I did! I now know for certain I won't be adding an O₂ cylinder input to my skimmer while using SPS-level lighting! (Joking... never gave that serious thought!)