Skimmer causing pH to DROP

[miggs76]

How is this possible? Everyday I turn my skimmer off for a few hours. When I turn it back on after a few hours I notice that the pH actually DROPS. I have a Neptune pH probe and it is calibrated. This happens while the lights are on, so it isn't just a coincidence that the pH is dropping as the lights are going off. Any thoughts?

 

[tankstudy]

I would guess that your skimmer is probably sucking in a ton of CO2 and mixing it into your water.

 

[aaron23]

i would recalibrate your ph probe... a skimmer only oxygenates the water.

 

[tankstudy]

i would recalibrate your ph probe... a skimmer only oxygenates the water.

It actually depends on what his/her CO2 concentrations are in the house. I've seen a few incidences in which people invite a ton of people over and the massive CO2 increase causes their tanks to drop in pH during the day.

 

[Randy Holmes-Farley]

It actually depends on what his/her CO2 concentrations are in the house. I've seen a few incidences in which people invite a ton of people over and the massive CO2 increase causes their tanks to drop in pH during the day.

That's correct.

A skimmer can raise or lower pH depending on whether the tank has an excess or deficit of CO2 relative to the aquarium water.

 

[Downbeach]

Through gas exchange, the skimmer will cause the CO2 to reach equilibrium with the surrounding atmosphere. So, if there's more CO2 in the surrounding air, then more will be introduced into the tank, lowering the pH, conversely if there's more CO2 in the tank, then the CO2 will diminish in the tank, elevating the pH.

 

[Randy Holmes-Farley]

i would recalibrate your ph probe... a skimmer only oxygenates the water.

FWIW, pH is not directly related to oxygen, only carbon dioxide and alkalinity. Most of the time, a skimmer will increase O2, but it can also lower it if the O2 is supersaturated relative to the air due to production of O2 during photosynthesis.

 

[miggs76]

probe has been recalibrated a few times. That is not the issue. Thanks for the replies though. Could there be any other reason? Tank is in the basement. Open top cube, plenty of flow (sps tank).

 

[Downbeach]

CO2 is the main culprit, can you run and air line from your skimmers air intake to an outside air source?

 

[Randy Holmes-Farley]

probe has been recalibrated a few times. That is not the issue. Thanks for the replies though. Could there be any other reason? Tank is in the basement. Open top cube, plenty of flow (sps tank).

Any other reason for what? pH declining when skimming?

pH is determined mathematically by the carbon dioxide level in the water and the carbonate alkalinity. Nothing else. So any process that impacts pH does it directly or indirectly through one or both of those two things.

Skimmers don't generally impact alkalinity, so direct changes in carbon dioxide would be the most immediate impact. Removing organics before they can break down to CO2 is another. Any other effect is not likely going to happen in the time frame you are noticing (such as impacts on photosynthesis from available nutrients, etc.).

 

[Robthorn]

I agree with everyone here that says your house has too much co2.
Take a glass of your tank water outside. Put an air stone attached to an air pump in the water for 15 minutes. Test the ph of the water in the glass right away. If the ph is higher then you have too much co2 in the house. Somehow ventilate your house.
Problem will be solved.

 

[Paulwizal23]

FWIW, pH is not directly related to oxygen, only carbon dioxide and alkalinity. Most of the time, a skimmer will increase O2, but it can also lower it if the O2 is supersaturated relative to the air due to production of O2 during photosynthesis.

Will a air drive. Protein skimmer increase higher PH the. The average needle nose skimmers like the NuvoSkim skimmer

 

[Randy Holmes-Farley]

Will a air drive. Protein skimmer increase higher PH the. The average needle nose skimmers like the NuvoSkim skimmer

I couldn't say what types of skimmers currently available do the best job aerating the water.

 

[arking_mark]

You might find this interesting...

Tuning a Skimmer / CO2 Scrubber for pH Control

On my reefing journey, I found Kalkwasse + Skimmer + CO2 Scrubber to be very effective for bringing my pH from 7.8 - 7.9 to 8.26 - 8.36. I guess most people would just leave it at that. However, I wanted to be more efficient with the CO2 scrubbing material so I wanted to implement a...

www.reef2reef.com

 

[Breadman03]

probe has been recalibrated a few times. That is not the issue. Thanks for the replies though. Could there be any other reason? Tank is in the basement. Open top cube, plenty of flow (sps tank).

Grab an air CO2 meter. It will tell you how much CO2 you have around the tank. Perhaps you could run an air line outside, even just temporarily. I have no idea how good this one is, but it was the first result.

Robot or human?

 

[Randy Holmes-Farley]

Grab an air CO2 meter. It will tell you how much CO2 you have around the tank. Perhaps you could run an air line outside, even just temporarily. I have no idea how good this one is, but it was the first result.

Robot or human?

A simple pH test can also do that assessment:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

 

[Cory]

Durring photosynthesis algae/phyto or corals raise ph durring the day by removing dissolved co2. The ph will rise from this effect. If the rate of photosynthesis is quicker than co2 gas can enter the water what happens is the ph will rise. But if your homes co2 is higher than outdoor air, then adding a skimmer will increase gas exchange and photosynthesis will not be able to keep rising the ph because the skimmer is working faster than before. So ph declines. But if you open your windows and doors. Ph will balance around 8.1