Experiments on pH, photoperiod and gas exchange. I gave up to skimmers

KonradTO

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Hi all,
In the last 3 weeks I did some experimenting on my 32g DT+ 15g fuge, and I think you might find interesting my results.
For those in a hurry here's a quick sumup of the post:
BEFORE LOW PH-->ADDED AIRSTONE AND MORE WATER MOVEMENT-->NOT ENOUGH--> MORE LIGHTS= MORE PH SWING-->FUNKY SKIMMER SETTING-->YAY, SUCCESS!
LOOK AT GRAPH BELOW :D

A bit of background:
After months of measuring pH by bringing vials of water to work (where I can access a lab) and getting low reads (7.6-7.8 throughout the day), I decided to explore more the pH issue since my corals were not doing very well and I had a massive dinoflagellate problem.
Many people told me that chasing pH was pointless but at the same time I was reading here in the forum that higher pH and temperatures might help with Amphidinium,

Therefore I purchased a 30$ pH probe and connected to my reef-pi controller.
First thing I did was measuring pH in tank, and after 1h in a well aerated cup. I clearly had a problem in gas exchange since my pH in tank was 7.6 and after aeration was 8.1 (!!).
Then I added an airstone in the sump connected to an air pump placed outside, added another wavemaker and monitored pH.
Situation was improving, but not enough. My daily pH was reaching at max 7.8 with all that water movement added and the airstone.

But what about ligh then? I knew my pH was reaching the highest value when my DT lights were ramping down. This meant that if I was running my lights more I would have depleted more CO2 with photosynthesis, and therefore increased my pH. Maybe my problem was a too short photoperiod?
Over the next couple of days I increased my blue lights from 8 to 12h and white lights from 6 to 8h. It was risky due to dinoflagellates but... I observed an increase in the max value of pH, up until 8.1 (YES!).. BUT also my bottom value was decreasing (all the way back to 7.6 , OUCH!). Basically I made my pH swing more pronounced in some way. Algae were consuming CO2 during the day, but this was followed by more intense cellular respiration I guess, which resulted in much higher pH swings.

I had to get rid of the excess CO2 if I wanted to increase my pH. In fact, like Randy explained very well in his articles, in presence of decent values of kH (> 7 dkH) the only reason for acidification can be CO2 excess in our tanks or in our houses.
After almost 1 year of reefing, I gave up and got myself a (cheap) skimmer. My problem was that I did not want to reduce my available nutrients though (dinos, remember?) , so I connected the skimmer with the drain open, flushing constantly the super wet skimmate back to the sump. In this way I avoided any possible bacteria proliferation in the skimmer cup, avoiding to alter the nutrient balance at the same time. Also the skimmer air intake was placed outside of the window.
20220716_125354.jpg

In the meanwhile,I started to see Ostreopsis in my tank as well, but with the silicate dosing I noticed Amphidinium was growing slower. What to do?
I always solved Ostreopsis problems with UV+blackout and I knew some people found blackouts helpful with Amphidinium when performed in the last phases of the recession. So I proceeded with a blackout, and turned the skimmer on. It was a perfect occasion to see the effect of the skimmer on the CO2 content of the water, without the interference of the photosythesys.

ph grafico.JPG

Moreover, as additional mesure to prevent poor gas exchange, I modified my acrylic lid and made a mesh lid instead.
As you can see, the pH started almost immediatly to rise despite the lack of photosynthesis. The gap in pH between 7.6 and 8 was ALL caused by CO2 trapped in the water.
Once 3days-blackout was over I slowly started to ramp up my lights again. You can see that the day/night swing is almost gone and pH keeps increasing as my lights come back to normal intensity.
Now my pH hovers between 8.05 and 8.15. Not perfect but I am satisfied, as it will probably increase with dosing once I will have more sps corals consuming kH.

I hope it was not a boring post. My suggestion for those struggling with pH is to get a cheap skimmer (mine was 80$) and place the air intake outside if you can, otherwise use a CO2 scrubber connected to the air intake. Somehow I resisted to the skimmer idea until now because I never had problems with nutrient export with the fuge. On the contrary I always struggled to keep nitrates up enough. But I think that a setting like mine is not affecting nutrients and the increased gas exchange can only improve the quality of the water. I thought I had enough gas exchange with a lot of surface movement, but apparently wasn't enough for some reason.
I cannot tell if it was because of the pH or because of the silicate dosing dealing with the Amphidinium, but since I added the skimmer all the corals seems happier and "plump". I have seen almost no growth in months and now I finally noticed some new zoa heads coming out from the plugs. It might be a combination of the 2, or simply my tank finally reaching stability, but my tank looks much better now.
IMG_20220717_123944.jpg
 
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Dan_P

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Hi all,
In the last 3 weeks I did some experimenting on my 32g DT+ 15g fuge, and I think you might find interesting my results.
For those in a hurry here's a quick sumup of the post:
BEFORE LOW PH-->ADDED AIRSTONE AND MORE WATER MOVEMENT-->NOT ENOUGH--> MORE LIGHTS= MORE PH SWING-->FUNKY SKIMMER SETTING-->YAY, SUCCESS!
LOOK AT GRAPH BELOW :D

A bit of background:
After months of measuring pH by bringing vials of water to work (where I can access a lab) and getting low reads (7.6-7.8 throughout the day), I decided to explore more the pH issue since my corals were not doing very well and I had a massive dinoflagellate problem.
Many people told me that chasing pH was pointless but at the same time I was reading here in the forum that higher pH and temperatures might help with Amphidinium,

Therefore I purchased a 30$ pH probe and connected to my reef-pi controller.
First thing I did was measuring pH in tank, and after 1h in a well aerated cup. I clearly had a problem in gas exchange since my pH in tank was 7.6 and after aeration was 8.1 (!!).
Then I added an airstone in the sump connected to an air pump placed outside, added another wavemaker and monitored pH.
Situation was improving, but not enough. My daily pH was reaching at max 7.8 with all that water movement added and the airstone.

But what about ligh then? I knew my pH was reaching the highest value when my DT lights were ramping down. This meant that if I was running my lights more I would have depleted more CO2 with photosynthesis, and therefore increased my pH. Maybe my problem was a too short photoperiod?
Over the next couple of days I increased my blue lights from 8 to 12h and white lights from 6 to 8h. It was risky due to dinoflagellates but... I observed an increase in the max value of pH, up until 8.1 (YES!).. BUT also my bottom value was decreasing (all the way back to 7.6 , OUCH!). Basically I made my pH swing more pronounced in some way. Algae were consuming CO2 during the day, but this was followed by more intense cellular respiration I guess, which resulted in much higher pH swings.

I had to get rid of the excess CO2 if I wanted to increase my pH. In fact, like Randy explained very well in his articles, in presence of decent values of kH (> 7 dkH) the only reason for acidification can be CO2 excess in our tanks or in our houses.
After almost 1 year of reefing, I gave up and got myself a (cheap) skimmer. My problem was that I did not want to reduce my available nutrients though (dinos, remember?) , so I connected the skimmer with the drain open, flushing constantly the super wet skimmate back to the sump. In this way I avoided any possible bacteria proliferation in the skimmer cup, avoiding to alter the nutrient balance at the same time. Also the skimmer air intake was placed outside of the window.
20220716_125354.jpg

In the meanwhile,I started to see Ostreopsis in my tank as well, but with the silicate dosing I noticed Amphidinium was growing slower. What to do?
I always solved Ostreopsis problems with UV+blackout and I knew some people found blackouts helpful with Amphidinium when performed in the last phases of the recession. So I proceeded with a blackout, and turned the skimmer on. It was a perfect occasion to see the effect of the skimmer on the CO2 content of the water, without the interference of the photosythesys.

ph grafico.JPG

Moreover, as additional mesure to prevent poor gas exchange, I modified my acrylic lid and made a mesh lid instead.
As you can see, the pH started almost immediatly to rise despite the lack of photosynthesis. The gap in pH between 7.6 and 8 was ALL caused by CO2 trapped in the water.
Once 3days-blackout was over I slowly started to ramp up my lights again. You can see that the day/night swing is almost gone and pH keeps increasing as my lights come back to normal intensity.
Now my pH hovers between 8.05 and 8.15. Not perfect but I am satisfied, as it will probably increase with dosing once I will have more sps corals consuming kH.

I hope it was not a boring post. My suggestion for those struggling with pH is to get a cheap skimmer (mine was 80$) and place the air intake outside if you can, otherwise use a CO2 scrubber connected to the air intake. Somehow I resisted to the skimmer idea until now because I never had problems with nutrient export with the fuge. On the contrary I always struggled to keep nitrates up enough. But I think that a setting like mine is not affecting nutrients and the increased gas exchange can only improve the quality of the water. I thought I had enough gas exchange with a lot of surface movement, but apparently wasn't enough for some reason.
I cannot tell if it was because of the pH or because of the silicate dosing dealing with the Amphidinium, but since I added the skimmer all the corals seems happier and "plump". I have seen almost no growth in months and now I finally noticed some new zoa heads coming out from the plugs. It might be a combination of the 2, or simply my tank finally reaching stability, but my tank looks much better now.
IMG_20220717_123944.jpg
Not boring at all. The happy ending was nice to see.
 

arking_mark

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Just a quick note on pH and Skimmers sizing.

Skimmers play a role in tank aeration and are just one tool in the CO2/pH equation for your tank.

Skimmers increase aeration with the air intake. Indoor air will be high in CO2 and outdoor air or CO2 scrubbed air lower in CO2.

Sizing the skimmer to increase pH will be dependent on other factors in your tank.

If we just focus on aeration, the effective CO2 in your tank will be aeration from return pumps, powerheads, and Skimmer. While your skimmer is bringing in lower CO2 air it may not be sufficient to overcome the aeration from the high CO2 indoor air that your return pumps and powerheads are aerating with.

In my tank, the return pump and powersheads provide about 40-50x turnover flow for the tank. Using a correctly sized skimmer had only a small impact on pH. When I went to a skimmer that was built for tanks 3 to 5 times my tank size, I was able to control pH in my tank (along with Kalkwasser and reverse lighting fuge).
 
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KonradTO

KonradTO

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Just a quick note on pH and Skimmers sizing.

Skimmers play a role in tank aeration and are just one tool in the CO2/pH equation for your tank.

Skimmers increase aeration with the air intake. Indoor air will be high in CO2 and outdoor air or CO2 scrubbed air lower in CO2.

Sizing the skimmer to increase pH will be dependent on other factors in your tank.

If we just focus on aeration, the effective CO2 in your tank will be aeration from return pumps, powerheads, and Skimmer. While your skimmer is bringing in lower CO2 air it may not be sufficient to overcome the aeration from the high CO2 indoor air that your return pumps and powerheads are aerating with.

In my tank, the return pump and powersheads provide about 40-50x turnover flow for the tank. Using a correctly sized skimmer had only a small impact on pH. When I went to a skimmer that was built for tanks 3 to 5 times my tank size, I was able to control pH in my tank (along with Kalkwasser and reverse lighting fuge).
Right. I forgot to mention that in my case the indoor CO2 levels must be excluded as a potential cause of low pH (in summer at least), but rather the limited gas exchange in the tank. I say this because I have 3 huge windows in the room where the tank is, and I kept those fully open 24/7 for a month or so. A lot of air circulation as well, as it is a bit breezy here. The cup aeration test I did was performed indoor.
Also having an acrylic lid reduced the gas exchange to some extent I suppose, so the last bit of increase in pH in the graph could be because of the different lid.
 
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KonradTO

KonradTO

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For the winter I think I will have to either use a recirculating CO2 scrubber or make some sort of acrylic "shield" for one of the windows so I can pipe the airline outside, but at the same time I won't waste precious heat in the house.
I was thinking about a double layer of acrylic panes sealed with insulating foam (drilling the window is not possible as I am renting)
 

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I’ve always wanted to try routing the skimmate back to the tank. Sometimes I think my oversized skimmer makes my tank too clean although it’s run pretty dry. Do you plan on leaving your skimmer like that or just until your nutrients go back up?
 
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KonradTO

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I’ve always wanted to try routing the skimmate back to the tank. Sometimes I think my oversized skimmer makes my tank too clean although it’s run pretty dry. Do you plan on leaving your skimmer like that or just until your nutrients go back up?
Good question. I have not decided yet. Actually after the last blackout for the first time my nitrates reached 20-25 ppm. But since I have no sps for now I am happy with that, better than zero.
I think that I will try to avoid it at every cost, but if for some reason I need to reduce the nutrients I can always temporarily dry skim and drain in a cannister.
 

taricha

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Algae were consuming CO2 during the day, but this was followed by more intense cellular respiration I guess, which resulted in much higher pH swings.
This is a good point that we gloss over. I remember reading that too much algae growth in a particular area prevented larvae of some crab or similar from surviving, and they said it was due to O2 depletion in the beds. Made little sense at the time.
But what you said is right. Cellular respiration continues at night when O2 producing photosynthesis stops. I once put a little piece of cyano mat in a sealed tube of tank water. In the light it oxygenated the water, and in the dark it depleted O2 from the water.

Makes sense that driving algae harder could increase the pH in the day and swing it harder down low at night.
 
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KonradTO

KonradTO

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This is a good point that we gloss over. I remember reading that too much algae growth in a particular area prevented larvae of some crab or similar from surviving, and they said it was due to O2 depletion in the beds. Made little sense at the time.
But what you said is right. Cellular respiration continues at night when O2 producing photosynthesis stops. I once put a little piece of cyano mat in a sealed tube of tank water. In the light it oxygenated the water, and in the dark it depleted O2 from the water.

Makes sense that driving algae harder could increase the pH in the day and swing it harder down low at night.
I think there is a lot of unexplored "space" in the hobby when it comes to the balance between CO2, lights and nutrients between DT and fuge.
 

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