Low pH & Alkalinity in Sterile Nano Tanks (Basement Setup)

[Skunk_Works]

Both my display and QT tanks have stabilized around pH 7.7–7.8 and dKH 6.7. Despite strong surface agitation and a powerful air stone running nonstop, I’ve seen no pH improvement.

When I opened windows and ran an exhaust fan, pH increased slightly — confirming my suspicion of high indoor CO₂ (I’ll verify this with an air monitor tomorrow). Both tanks sit in a basement, which likely limits fresh air exchange.

They’re currently sterile systems aside from copepods. My QT tank is finishing its cycle, and I’ll soon add two clownfish for observation.

I know Tropic Marin Pro Reef mixes low in alkalinity, so these numbers aren’t surprising, but I’d like a long-term plan for pH stability — especially through winter.

Considering:
Adding a skimmer to pair with a CO₂ scrubber. Any good recommendations for skimmers with powerful air draw capability that would fit an AIO?

Possibly running an outdoor air line (worried about freezing)

Gradually raising alkalinity before adding livestock

Would you address low pH and dKH now, or wait until the tanks mature and balance naturally?

Looking for data-driven or firsthand experience, especially from others running nano/AIO tanks in enclosed spaces

 

[P-Dub]

Both my display and QT tanks have stabilized around pH 7.7–7.8 and dKH 6.7. Despite strong surface agitation and a powerful air stone running nonstop, I’ve seen no pH improvement.

When I opened windows and ran an exhaust fan, pH increased slightly — confirming my suspicion of high indoor CO₂ (I’ll verify this with an air monitor tomorrow). Both tanks sit in a basement, which likely limits fresh air exchange.

They’re currently sterile systems aside from copepods. My QT tank is finishing its cycle, and I’ll soon add two clownfish for observation.

I know Tropic Marin Pro Reef mixes low in alkalinity, so these numbers aren’t surprising, but I’d like a long-term plan for pH stability — especially through winter.

Considering:
Adding a skimmer to pair with a CO₂ scrubber. Any good recommendations for skimmers with powerful air draw capability that would fit an AIO?

Possibly running an outdoor air line (worried about freezing)

Gradually raising alkalinity before adding livestock

Would you address low pH and dKH now, or wait until the tanks mature and balance naturally?

Looking for data-driven or firsthand experience, especially from others running nano/AIO tanks in enclosed spaces

Hi @Skunk_Works. I read through your situation and wanted to offer some insights and suggestions based on personal experience, research, and community experience.

You're definitely on the right track in identifying high indoor CO2 as a major contributor to your low pH. The fact that opening windows and running an exhaust fan raised your pH confirms this.
Naturally, this isn’t immediately dangerous, especially in a sterile system.
In the short term, I'd raise your Alk before adding livestock. Baking soda, soda ash, or even Kalkwasser can be used, depending on the parameters you'd like right now. This helps buffer pH and stabilize your system.

Once you get your air monitor, you’ll have a clearer picture. If indoor CO₂ is consistently high, consider running a CO₂ scrubber on your skimmer, ventilate the space periodically, and, if you have room, run a refugium or, if space is really tight, an algae scrubber, running either of the two on a reverse lighting schedule.

Some Skimmers you may consider are;
-MagTool N100 Plus - compact footprint, fits tight AIO setups
-IOAOI Nano Skimmer - fits smaller AIO chambers, hose-compatible
-Simplicity DC Skimmers - great performance, scrubber-friendly for nanos
-Bubble Magus Curve Series - Affordable and effective in smaller AIO systems
-Reef Octopus Classic 110-INT - Reliable, strong air draw, and scrubber compatible

Running an outdoor air line to feed your skimmer is effective but comes with caveats: Use insulated tubing or pull air from a vented attic to help deal with freezing conditions. Remember, though, the longer the tubing run, the larger the diameter tubing needed to facilitate unrestricted air flow. Add a carbon pre-filter to block pollutants like landscaping chemicals or exhaust fumes, etc. if pulling from the outdoors. If you really want to open a can of worms, search microbubble scrubbing and pulling CO2 scrubbed air from the exterior. I've done it all, even combined setups.

Since your tanks are sterile and, I'm assuming, just finishing their cycle, I would strongly consider raising your alkalinity now, as it’s foundational and will help stabilize pH in time. Directly addressing pH can wait if livestock isn’t present yet, but prepping now (via ventilation or scrubbers) will make things easier down the line.

You're doing everything right by approaching this methodically. Basement tanks are notoriously tricky due to poor air exchange, but with a combination of alkalinity control, CO₂ management, and equipment upgrades, you’ll be set up for success, even through winter.

 

[Australian_Reef]

I second everything above.

If you know your tank is always going to be struggling to keep an optimal ph I really can’t recommend kalkwasser enough for your future plans. So easy. . Definitely not the only way to do things but it’s cheap and simple especially for smaller tanks.

 

[Skunk_Works]

Both my display and QT tanks have stabilized around pH 7.7–7.8 and dKH 6.7. Despite strong surface agitation and a powerful air stone running nonstop, I’ve seen no pH improvement.

When I opened windows and ran an exhaust fan, pH increased slightly — confirming my suspicion of high indoor CO₂ (I’ll verify this with an air monitor tomorrow). Both tanks sit in a basement, which likely limits fresh air exchange.

They’re currently sterile systems aside from copepods. My QT tank is finishing its cycle, and I’ll soon add two clownfish for observation.

I know Tropic Marin Pro Reef mixes low in alkalinity, so these numbers aren’t surprising, but I’d like a long-term plan for pH stability — especially through winter.

Considering:
Adding a skimmer to pair with a CO₂ scrubber. Any good recommendations for skimmers with powerful air draw capability that would fit an AIO?

Possibly running an outdoor air line (worried about freezing)

Gradually raising alkalinity before adding livestock

Would you address low pH and dKH now, or wait until the tanks mature and balance naturally?

Looking for data-driven or firsthand experience, especially from others running nano/AIO tanks in enclosed spaces

Hi @Skunk_Works. I read through your situation and wanted to offer some insights and suggestions based on personal experience, research, and community experience.

You're definitely on the right track in identifying high indoor CO2 as a major contributor to your low pH. The fact that opening windows and running an exhaust fan raised your pH confirms this.
Naturally, this isn’t immediately dangerous, especially in a sterile system.
In the short term, I'd raise your Alk before adding livestock. Baking soda, soda ash, or even Kalkwasser can be used, depending on the parameters you'd like right now. This helps buffer pH and stabilize your system.

Once you get your air monitor, you’ll have a clearer picture. If indoor CO₂ is consistently high, consider running a CO₂ scrubber on your skimmer, ventilate the space periodically, and, if you have room, run a refugium or, if space is really tight, an algae scrubber, running either of the two on a reverse lighting schedule.

Some Skimmers you may consider are;
-MagTool N100 Plus - compact footprint, fits tight AIO setups
-IOAOI Nano Skimmer - fits smaller AIO chambers, hose-compatible
-Simplicity DC Skimmers - great performance, scrubber-friendly for nanos
-Bubble Magus Curve Series - Affordable and effective in smaller AIO systems
-Reef Octopus Classic 110-INT - Reliable, strong air draw, and scrubber compatible

Running an outdoor air line to feed your skimmer is effective but comes with caveats: Use insulated tubing or pull air from a vented attic to help deal with freezing conditions. Remember, though, the longer the tubing run, the larger the diameter tubing needed to facilitate unrestricted air flow. Add a carbon pre-filter to block pollutants like landscaping chemicals or exhaust fumes, etc. if pulling from the outdoors. If you really want to open a can of worms, search microbubble scrubbing and pulling CO2 scrubbed air from the exterior. I've done it all, even combined setups.

Since your tanks are sterile and, I'm assuming, just finishing their cycle, I would strongly consider raising your alkalinity now, as it’s foundational and will help stabilize pH in time. Directly addressing pH can wait if livestock isn’t present yet, but prepping now (via ventilation or scrubbers) will make things easier down the line.

You're doing everything right by approaching this methodically. Basement tanks are notoriously tricky due to poor air exchange, but with a combination of alkalinity control, CO₂ management, and equipment upgrades, you’ll be set up for success, even through winter.

Thank you for your detailed response and recommendations.

My goal from the outset has been to build this system for maximum stability with minimal complexity. I prefer to progress gradually, establishing a strong chemical and biological foundation rather than chasing numbers. For now, maintaining both alkalinity and pH stability remains the primary focus, and CO₂ appears to be the root issue at hand.

I’ll continue testing to determine the most effective way to raise alkalinity. Calcium levels are stable and within range, so I’m holding off on kalkwasser until biological demand increases. Once I’ve collected several days of CO₂ data, I’ll establish a baseline to better evaluate its effect on pH.

Your insights on ventilation and scrubber setups were especially helpful. Addressing those factors before introducing livestock should promote long-term equilibrium and stability through winter.

I have a Nature Dimensions roller filter on the way and am considering the Tunze 9001 skimmer for use with a CO₂ scrubber. The main challenge has been working within the size limits of the AIO chambers. I’ve been designing a custom media basket for the center chamber as the roller filter takes up the first. To accommodate media, heater and skimmer while maintaining optimal flow will be an enjoyable challenge, and I plan to document the final setup once complete. I’d love to have a refugium to further increase CO2 uptake but again am very limited in space.

It’s also worth noting that it seems many hobbyists overlook proper water level management in AIO systems. Keeping slightly lower levels in each chamber to create small “waterfalls” into the return section greatly improves flow and filtration efficiency, whereas filling the chambers completely can reduce both performance and surface agitation.

I’ll return here once more information becomes available.

Thanks again.

 

[Australian_Reef]

Thank you for your detailed response and recommendations.

My goal from the outset has been to build this system for maximum stability with minimal complexity. I prefer to progress gradually, establishing a strong chemical and biological foundation rather than chasing numbers. For now, maintaining both alkalinity and pH stability remains the primary focus, and CO₂ appears to be the root issue at hand.

I’ll continue testing to determine the most effective way to raise alkalinity. Calcium levels are stable and within range, so I’m holding off on kalkwasser until biological demand increases. Once I’ve collected several days of CO₂ data, I’ll establish a baseline to better evaluate its effect on pH.

Your insights on ventilation and scrubber setups were especially helpful. Addressing those factors before introducing livestock should promote long-term equilibrium and stability through winter.

I have a Nature Dimensions roller filter on the way and am considering the Tunze 9001 skimmer for use with a CO₂ scrubber. The main challenge has been working within the size limits of the AIO chambers. I’ve been designing a custom media basket for the center chamber as the roller filter takes up the first. To accommodate media, heater and skimmer while maintaining optimal flow will be an enjoyable challenge, and I plan to document the final setup once complete. I’d love to have a refugium to further increase CO2 uptake but again am very limited in space.

It’s also worth noting that it seems many hobbyists overlook proper water level management in AIO systems. Keeping slightly lower levels in each chamber to create small “waterfalls” into the return section greatly improves flow and filtration efficiency, whereas filling the chambers completely can reduce both performance and surface agitation.

I’ll return here once more information becomes available.

Thanks again.

I get you man. This is how I think too.

 

[P-Dub]

Like I said, you're on the right track — so keep chugging along.

I’d really recommend more research here on microbubble scrubbing. Implementing it on a reverse light schedule along with a CO₂ scrubber on the feed air to my bubble scrubber and skimmer, and having a successful refugium, helped tremendously to stabilize and raise overall pH levels, all without adding additional chemicals to the system.

At the time, we had four dogs (now five!) and two humans in a relatively tight, energy-efficient home in the extreme tropics, so indoor CO₂ was definitely a challenge. This combo made a noticeable difference.

 

[Australian_Reef]

Like I said, you're on the right track — so keep chugging along.

I’d really recommend more research here on microbubble scrubbing. Implementing it on a reverse light schedule along with a CO₂ scrubber on the feed air to my bubble scrubber and skimmer, and having a successful refugium, helped tremendously to stabilize and raise overall pH levels, all without adding additional chemicals to the system.

At the time, we had four dogs (now five!) and two humans in a relatively tight, energy-efficient home in the extreme tropics, so indoor CO₂ was definitely a challenge. This combo made a noticeable difference.

We have 4 kids and are in Queensland Australia so very similar! Not especially airtight house but in summer we have air recirculating and windows closed. Kalkwasser has been great. Obv when you have the Ca demand as you said skunk.

 

[mcarroll]

Both my display and QT tanks have stabilized around pH 7.7–7.8 and dKH 6.7.

That pH is not "too low" if those numbers are taken from the low end of your tank's range. But that dKH probably is too low....and a higher dKH will anchor your pH a bit higher.

What is the pH range you see between before lights-OUT and before lights-ON? (That's usually maximum and minimum.)

The alk and pH numbers posted would indicate CO2 levels much higher than 700 ppm....which is high enough to cause problems for humans. Will be interesting to see if your monitors has anything different or interesting to add.

(6.7 dKH is about equal to 2.4 meq/L.)

Folks worrying about their tank's pH need to worry about their own health.

As far as your tank is concerned, corals in particular, they aren't concerned with pH, and they appreciate plentiful CO2. There's literally nothing to worry about with the tank...but the tank's pH is still an indicator of atmospheric CO2.

So if CO2 levels in your household air are high enough to cause "low pH" then it may be high enough to worry about FOR YOUR HEALTH.

An HVAC professional can (and should) remedy this permanently.

Once I’ve collected several days of CO₂ data, I’ll establish a baseline to better evaluate its effect on pH.

So did you get any reading at all yet?

Trending we can wait for, but some data points would be nice!

 

[P-Dub]

Folks worrying about their tank's pH need to worry about their own health.

As far as your tank is concerned, corals in particular, they aren't concerned with pH, and they appreciate plentiful CO2. There's literally nothing to worry about with the tank...but the tank's pH is still an indicator of atmospheric CO2.

I really have to know where you are gleaning this information from.

 

[P-Dub]

@mcarroll While it's true that tank pH can reflect indoor CO2 levels, the claim that corals "aren’t concerned with pH and appreciate plentiful CO2" is actually scientifically inaccurate.


Corals are highly sensitive to both pH and CO₂ levels. Elevated CO2 lowers pH, which reduces carbonate ion availability, essential for coral calcification. Numerous peer-reviewed studies have shown that:

-High CO2 impairs coral growth and skeletal formation.
-Low pH stresses corals and can even dissolve their skeletons.
-Stable pH (typically 8.1–8.4) is critical for coral health in reef aquariums.

So yes, your tank’s pH does matter, not just as a CO2 indicator, but as a direct factor in coral vitality. Ignoring it risks long-term harm to your reef. The following are a few studies that support my claims.

*Kleypas & Langdon (2000): Found that increased CO₂ reduces carbonate ion concentration, leading to decreased calcification rates in corals and algae. [cales.arizona.edu]

*Hoegh-Guldberg et al. (2017): Demonstrated that coral reefs are highly vulnerable to ocean acidification and warming, with reduced calcification and increased bleaching. [frontiersin.org]

*Schoepf et al. (2013): Showed that elevated CO₂ significantly reduced calcification in some coral species, even when energy reserves were maintained. [journals.plos.org]

*Langdon et al. (2002): Long-term mesocosm experiments revealed that elevated CO₂ leads to reduced calcification in reef systems. [columbia.edu]

*Miami Reef (2025): pH below 7.7 can begin dissolving calcium carbonate, threatening coral skeletons. [reef2reef.com]

*Aquarium Specialty (2025): CO₂ scrubbers help maintain stable pH, improving coral growth and coloration. [aquariumsp...cialty.com]

*Institute for Environmental Research and Education (2025): Emphasizes the importance of maintaining pH between 8.1–8.4 for optimal coral health. [iere.org]

*Allemand, D. (2019). Les coraux et le changement climatique. Océan et Climat – Fiches scientifiques, p.3649. Available on: https://ocean-climate.org/wp-content/uploads/2019/09/Fiches-scientifiques-2019.pdf 

*Frankignoulle, M., & Gattuso, J.-P. (1993). Air-Sea CO2 Exchange in Coastal Ecosystems. In R. Wollast, F. T. Mackenzie, & L. Chou (Éds.), Interactions of C, N, P and S Biogeochemical Cycles and Global Change (p. 233248). Springer. https://doi.org/10.1007/978-3-642-76064-8_9 

*Gattuso, J.-P., Pichon, M., Delesalle, B., & Frankignoulle, M. (1993). Community metabolism and air-sea CO2 fluxes in a coral reef ecosystem (Moorea, French Polynesia). Marine Ecology Progress Series, 96, 259267. https://doi.org/10.3354/meps096259 

*Gattuso, J.-P., Frankignoulle, M., & Smith, S. V. (1999). Measurement of community metabolism and significance in the coral reef CO2 source-sink debate. Proceedings of the National Academy of Sciences of the United States of America, 96(23), 1301713022. 

*Kayanne, H., Suzuki, A., & Saito, H. (1995). Diurnal changes in the partial pressure of carbon dioxide in coral reef water. Science (New York, N.Y.), 269(5221), 214216. https://doi.org/10.1126/science.269.5221.214 

*Spalding M.D., Ravilious C., Green E.P. (2001) World Atlas of Coral Reefs. Prepared at the UNEP World Conservation Monitoring Center. University of California Press. Berkley, USA. Site internet : https://archive.org/details/worldatlasofcora01spal/page/2/mode/2up  

*Tambutté S.,  Holcomb, M. Ferrier-Pagès C., Reynaud S., Tambutté E.,  Zoccola D., & Allemand D.  (2011). Coral biomineralization: From the gene to the environment. Journal of Experimental Marine Biology and Ecology, 408(12), 5878. https://doi.org/10.1016/j.jembe.2011.07.026

*Tunnicliffe, V. (1983). Caribbean Staghorn Coral Populations : Pre-Hurricane Allen Conditions in Discovery Bay, Jamaica. Bulletin of Marine Science, 33(1), 132151. 

*Ware J. R., Smith S. V. & Reaka-Kudla M. L., 1992. Coral reefs: sources or sinks of atmospheric CO2? Coral Reefs 11:127-130. 

I truly tried to find data to support your claims. I could very well be looking in all the wrong places. So if you could cite a few studies that give weight to your assertion that, "Folks worrying about their tank's pH need to worry about their own health." and

"As far as your tank is concerned, corals in particular, they aren't concerned with pH, and they appreciate plentiful CO2. There's literally nothing to worry about with the tank...but the tank's pH is still an indicator of atmospheric CO2." I will stand humbly corrected.

I'm not trying to be pedantic or looking to bash you, and I know you are reaching out to help, and that is appreciated. I'm concerned that information may be detrimental. I really do want to know about the data to support pH and, to a greater degree, CO2 being inconsequential, if only because it stands in the face of conventional science. I believe in giving solid and accurate information to our fellow reefers to have the best strategies for success.

 

[Rocks reef]

Hi @Skunk_Works. I read through your situation and wanted to offer some insights and suggestions based on personal experience, research, and community experience.

You're definitely on the right track in identifying high indoor CO2 as a major contributor to your low pH. The fact that opening windows and running an exhaust fan raised your pH confirms this.
Naturally, this isn’t immediately dangerous, especially in a sterile system.
In the short term, I'd raise your Alk before adding livestock. Baking soda, soda ash, or even Kalkwasser can be used, depending on the parameters you'd like right now. This helps buffer pH and stabilize your system.

Once you get your air monitor, you’ll have a clearer picture. If indoor CO₂ is consistently high, consider running a CO₂ scrubber on your skimmer, ventilate the space periodically, and, if you have room, run a refugium or, if space is really tight, an algae scrubber, running either of the two on a reverse lighting schedule.

Some Skimmers you may consider are;
-MagTool N100 Plus - compact footprint, fits tight AIO setups
-IOAOI Nano Skimmer - fits smaller AIO chambers, hose-compatible
-Simplicity DC Skimmers - great performance, scrubber-friendly for nanos
-Bubble Magus Curve Series - Affordable and effective in smaller AIO systems
-Reef Octopus Classic 110-INT - Reliable, strong air draw, and scrubber compatible

Running an outdoor air line to feed your skimmer is effective but comes with caveats: Use insulated tubing or pull air from a vented attic to help deal with freezing conditions. Remember, though, the longer the tubing run, the larger the diameter tubing needed to facilitate unrestricted air flow. Add a carbon pre-filter to block pollutants like landscaping chemicals or exhaust fumes, etc. if pulling from the outdoors. If you really want to open a can of worms, search microbubble scrubbing and pulling CO2 scrubbed air from the exterior. I've done it all, even combined setups.

Since your tanks are sterile and, I'm assuming, just finishing their cycle, I would strongly consider raising your alkalinity now, as it’s foundational and will help stabilize pH in time. Directly addressing pH can wait if livestock isn’t present yet, but prepping now (via ventilation or scrubbers) will make things easier down the line.

You're doing everything right by approaching this methodically. Basement tanks are notoriously tricky due to poor air exchange, but with a combination of alkalinity control, CO₂ management, and equipment upgrades, you’ll be set up for success, even through winter.

Spot on and great advice/feedback!

 

[mcarroll]

I truly tried to find data to support your claims.

"My claim" isn't unique, or really even mine: Don't chase pH.

You may be looking too hard if you aren't finding anything. Check out the articles section here on R2R:
Beginner Topic Why Chasing pH is a Trap for Beginner Reefkeepers

If you want to know why *we* might care about pH, Randy's more recent article says it very well:
pH And The Reef Aquarium (2019; the discussion section veers into "my claim" as early as post #3)

I can say I've tried to do my part as a volunteer to spread the knowledge. (* here, on nano-reef, and on reefsuccess.com which is also in the sig of every post I make) There's a usable search function on my site to look for a term like CO2. (I recommend looking at everything in the linked search.) Let me know if you still don't find what you're looking for.

There are too many good articles on the subject of basic reef tank chemistry by Randy and others to even try to address that in someone's thread. Here is one great one:
Reef Aquarium Water Parameters

Numerous peer-reviewed studies have shown that:

-High CO2 impairs coral growth and skeletal formation.
-Low pH stresses corals and can even dissolve their skeletons.
-Stable pH (typically 8.1–8.4) is critical for coral health in reef aquariums.

This is not the current state of knowledge. Multiple journal articles you can find on that reefsuccess.com search will clear this up.

But here are a couple of shortcuts:
First, we've known since at least 2009 that corals have an incredible ability (tho not unlimited) to deal with changes in water quality around them.

The authors combine a lot of this information and test the limits of what corals can tolerate here:
Why Corals Care About Ocean Acidification: Uncovering the Mechanism (2009)

Last, skeleton formation was found to be independent of pH in 2017:

Biological control of aragonite formation in stony corals

Biological control of aragonite formation in stony corals Stanislas Von Euw1, Qihong Zhang, Viacheslav Manichev, Nagarajan Murali, Juliane Gross, Leonard C. Feldman, Torgny Gustafsson, Carol Flach,…

reefsuccess.com

Both of those ought to be for anyone who hasn't bumped into this information yet....keeping in mind that our corals don't have the same limitations as corals in the ocean.

One key quote for our thread from the 2017 article:

Last, our results strongly suggest that the ability of corals to calcify is biologically controlled and thus relatively robust. As such, the biological reaction is far from thermodynamic equilibrium, and, hence, biomineralization in stony corals is not simply related to physicochemical parameters such as the equilibrium saturation state of carbonate ions or the bulk pH of seawater (33).

Skeletal density and growth rate are two common refrains on the topic...things which have been found to be "affected by low pH". (HINT: The tests in these articles were not good simulations of a tank environment; that wasn't part of their testing.)

Do less-massive skeletons automatically mean "unhealthy"?
No. Corals reproduce sexually AND vegetatively. A less dense skeleton makes natural fragging more likely. It is a life strategy under historically-predictable circumstances for them. (CO2 levels have historically been both much higher and much lower than today through the history of corals....through the current lives of some of the older corals out there!)

Does slower growth automatically mean "unhealthy"?
No. It might be surprising, but faster growth is actually associated with lower fitness factors such as slower wound healing.

What makes some of these studies I've linked especially of note is that some take care to implement a few of the controls we as aquarists (reefkeepers!) would use to keep corals healthy – eg feeding and NO3/PO4 dosing – and they see the same positive results we see.

Their positive results in the 2009 article reminded me of the findings in this 2018 posting:

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Article Link: Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates Authors: Rosset, S., et al. Journal: Marine Pollution Bulletin (2017)…

reefsuccess.com

@P-Dub, the truth is that folks make LOTS of assumptions about whether their corals are "happy" or "unhappy". Most of it is very unscientific. And in some cases what used to be thought correct turns out to have a different story. As it turns out, corals (and other calcium precipitators like clams and snails) have the proper "gearing" to deal with the up's ad down's associated with oceanic levels of pH....it's not something they worry about.

---

@Skunk_Works, we are unfortunately glossing over the human health angle just to dwell on the (in)validity of chasing pH numbers.

At high enough CO2 levels to cause anything that could be considered "a pH problem" in a reef tank – look again Randy's chart I pasted into post #8 – either CO2 or alkalinity would have to be pretty drastically off.

To get your reported pH of 7.7 to 7.8, alkalinity could have cratered to under 0.75 meq/L (< 2 dKH) on the chart – but it doesn't seem like there's any current suspicion of a drastic alkalinity issue.

Looking again at the chart in post #8, even 700 ppm CO2 will only drop the equilibrium point of seawater to 7.95 or so; not THAT far from 8.1.

*** Atmospheric CO2 being in excess (≥1000 ppm) needs to be ruled out IMO.

Please start with Randy's aeration test.
The numbers need confirming (eg with a CO2 monitor) but numbers like these point to a CO2 concentration four digits long. If you are unfamiliar, look up the effects of 1000 ppm and 2000 ppm CO2 on human health and sleep. It's only a benefit if you're photosynthetic!

In case it's not a household issue, good ventilation is crucial in the room where the tank is as well as the house. So don't keep the fish room too sealed up. In the old days, all houses had "good ventilation" whether it was desired or not. Modern building methods can cause CO2 to build up though.

If you do confirm excessive CO2 but there are no simple remedies like opening the room more, consider getting a professional opinion on changing your HVAC setup. It could be just an adjustment, or it could be some new equipment....totally depends on your actual situation. Treating just the tank in this situation (ie CO2 > 1000 ppm) is unproductive and unwise.

 

[P-Dub]

I truly tried to find data to support your claims.

"My claim" isn't unique, or really even mine: Don't chase pH.

You may be looking too hard if you aren't finding anything. Check out the articles section here on R2R:
Beginner Topic Why Chasing pH is a Trap for Beginner Reefkeepers

If you want to know why *we* might care about pH, Randy's more recent article says it very well:
pH And The Reef Aquarium (2019; the discussion section veers into "my claim" as early as post #3)

I can say I've tried to do my part as a volunteer to spread the knowledge. (* here, on nano-reef, and on reefsuccess.com which is also in the sig of every post I make) There's a usable search function on my site to look for a term like CO2. (I recommend looking at everything in the linked search.) Let me know if you still don't find what you're looking for.

There are too many good articles on the subject of basic reef tank chemistry by Randy and others to even try to address that in someone's thread. Here is one great one:
Reef Aquarium Water Parameters

Numerous peer-reviewed studies have shown that:

-High CO2 impairs coral growth and skeletal formation.
-Low pH stresses corals and can even dissolve their skeletons.
-Stable pH (typically 8.1–8.4) is critical for coral health in reef aquariums.

This is not the current state of knowledge. Multiple journal articles you can find on that reefsuccess.com search will clear this up.

But here are a couple of shortcuts:
First, we've known since at least 2009 that corals have an incredible ability (tho not unlimited) to deal with changes in water quality around them.

The authors combine a lot of this information and test the limits of what corals can tolerate here:
Why Corals Care About Ocean Acidification: Uncovering the Mechanism (2009)

Last, skeleton formation was found to be independent of pH in 2017:

Biological control of aragonite formation in stony corals

Biological control of aragonite formation in stony corals Stanislas Von Euw1, Qihong Zhang, Viacheslav Manichev, Nagarajan Murali, Juliane Gross, Leonard C. Feldman, Torgny Gustafsson, Carol Flach,…

reefsuccess.com

Both of those ought to be for anyone who hasn't bumped into this information yet....keeping in mind that our corals don't have the same limitations as corals in the ocean.

One key quote for our thread from the 2017 article:

Last, our results strongly suggest that the ability of corals to calcify is biologically controlled and thus relatively robust. As such, the biological reaction is far from thermodynamic equilibrium, and, hence, biomineralization in stony corals is not simply related to physicochemical parameters such as the equilibrium saturation state of carbonate ions or the bulk pH of seawater (33).

Skeletal density and growth rate are two common refrains on the topic...things which have been found to be "affected by low pH". (HINT: The tests in these articles were not good simulations of a tank environment; that wasn't part of their testing.)

Do less-massive skeletons automatically mean "unhealthy"?
No. Corals reproduce sexually AND vegetatively. A less dense skeleton makes natural fragging more likely. It is a life strategy under historically-predictable circumstances for them. (CO2 levels have historically been both much higher and much lower than today through the history of corals....through the current lives of some of the older corals out there!)

Does slower growth automatically mean "unhealthy"?
No. It might be surprising, but faster growth is actually associated with lower fitness factors such as slower wound healing.

What makes some of these studies I've linked especially of note is that some take care to implement a few of the controls we as aquarists (reefkeepers!) would use to keep corals healthy – eg feeding and NO3/PO4 dosing – and they see the same positive results we see.

Their positive results in the 2009 article reminded me of the findings in this 2018 posting:

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Article Link: Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates Authors: Rosset, S., et al. Journal: Marine Pollution Bulletin (2017)…

reefsuccess.com

@P-Dub, the truth is that folks make LOTS of assumptions about whether their corals are "happy" or "unhappy". Most of it is very unscientific. And in some cases what used to be thought correct turns out to have a different story. As it turns out, corals (and other calcium precipitators like clams and snails) have the proper "gearing" to deal with the up's ad down's associated with oceanic levels of pH....it's not something they worry about.

---

@Skunk_Works, we are unfortunately glossing over the human health angle just to dwell on the (in)validity of chasing pH numbers.

At high enough CO2 levels to cause anything that could be considered "a pH problem" in a reef tank – look again Randy's chart I pasted into post #8 – either CO2 or alkalinity would have to be pretty drastically off.

To get your reported pH of 7.7 to 7.8, alkalinity could have cratered to under 0.75 meq/L (< 2 dKH) on the chart – but it doesn't seem like there's any current suspicion of a drastic alkalinity issue.

Looking again at the chart in post #8, even 700 ppm CO2 will only drop the equilibrium point of seawater to 7.95 or so; not THAT far from 8.1.

*** Atmospheric CO2 being in excess (≥1000 ppm) needs to be ruled out IMO.

Please start with Randy's aeration test.
The numbers need confirming (eg with a CO2 monitor) but numbers like these point to a CO2 concentration four digits long. If you are unfamiliar, look up the effects of 1000 ppm and 2000 ppm CO2 on human health and sleep. It's only a benefit if you're photosynthetic!

In case it's not a household issue, good ventilation is crucial in the room where the tank is as well as the house. So don't keep the fish room too sealed up. In the old days, all houses had "good ventilation" whether it was desired or not. Modern building methods can cause CO2 to build up though.

If you do confirm excessive CO2 but there are no simple remedies like opening the room more, consider getting a professional opinion on changing your HVAC setup. It could be just an adjustment, or it could be some new equipment....totally depends on your actual situation. Treating just the tank in this situation (ie CO2 > 1000 ppm) is unproductive and unwise.

Nope, I still have not found a single peer reviewed article that backs your claim that CO2 levels are inconsequential to coral growth or health. Or that they love abundant CO2.

 

[mcarroll]

Nope, I still have not found a single peer reviewed article that backs your claim that CO2 levels are inconsequential to coral growth or health. Or that they love abundant CO2.

LOL....3 minutes? At least I know I can add you to my special list of gifted reefers now.

 

[P-Dub]

Nope, I still have not found a single peer reviewed article that backs your claim that CO2 levels are inconsequential to coral growth or health. Or that they love abundant CO2.

LOL....3 minutes? At least I know I can add you to my special list of gifted reefers now.

Well, that's uncalled for and quite petty.

My issue with your claim is not about chasing numbers, as I have addressed that numerous times already in my response posts. The bulk of my concern with your apparent false claims is that CO2 is inconsequential to coral growth or health, and that they love abundant CO2. I don't need to waste any more of my time on nonsensical claims such as that. I have already exhausted an unreasonable amount of time looking for peer-reviewed articles to back YOUR claim. If you're unwilling to do that yourself and present the data necessary to lend support to your false claims, that's fine, but you don't need to be mean or nasty because I point out your inadequacies.

You can put me on whatever list you would like, and it makes clear what type of person you are.

I wish you all the best of luck.

 

[Skunk_Works]

Hello. Update to the PH situation.
I got my air monitor and conducted a test by shutting windows and doors and working in the room for 2 hours. CO2 levels rose to 1500 , it’s estimated that overnight it could reach levels of 5000+. I now leave the door open and window cracked at all times.

CO2 levels now range from 450 - 800 max.

Both tanks PH rose immediately and have steadied at 7.9 and 8.0.

I also have figured out the tropic Marin pro reef salt mixes to a DKH of 7.2 - something.

Long story short I used baking soda + RODI mix to experimentally raise my QT tank DKH. it’s PH is stable at 8.

I’m going to add a CO2 scrubber im the future when I buy a skimmer.

My first clownfish arrive this Thursday and are going to live in the QT for observation. Buying from dr. Reef.

 

[mcarroll]

Hello. Update to the PH situation.
I got my air monitor and conducted a test by shutting windows and doors and working in the room for 2 hours. CO2 levels rose to 1500 , it’s estimated that overnight it could reach levels of 5000+. I now leave the door open and window cracked at all times.

CO2 levels now range from 450 - 800 max.

Both tanks PH rose immediately and have steadied at 7.9 and 8.0.

Wow – thanks for posting that data!!

Great that things straightened out immediately!

Other folks that did corrections like this felt their sleep being better...seems to be a common thread. Anything seem "better" like that?

Is opening windows practical year round where you are? In that case you have your solution!

Otherwise you can probably get a free estimate from an HVAC place to find out what would be needed to remedy this at the HVAC level. Might be as simple as a damper adjustment, but totally depends on your actual HVAC and duct installation. IMO probably worth finding out at least.

 

[Skunk_Works]

I’m in Colorado, so the window is only slightly cracked , but by keeping the door open to the much larger room outside this one, it’s seemed to fix the issue.

We will see how this goes throughout the winter.

I will be moving in the near future and will take ventilation into consideration when choosing a home and tank placement.

For now I will continue to minor the water chemistry and explore my options to finding stability.

As of now I still do not have any corals , I’m taking it very slowly.

Thanks for your input !

 

[mcarroll]

That is excellent if something is simple as opening the door to the fish room can make a difference for you.

Simply adding a fan to blow air in or out of that room may help further.... but I would have to imagine just having the door open could be enough. Probably not even a need for a CO2 scrubber.

 

[Australian_Reef]

Hello. Update to the PH situation.
I got my air monitor and conducted a test by shutting windows and doors and working in the room for 2 hours. CO2 levels rose to 1500 , it’s estimated that overnight it could reach levels of 5000+. I now leave the door open and window cracked at all times.

CO2 levels now range from 450 - 800 max.

Both tanks PH rose immediately and have steadied at 7.9 and 8.0.

I also have figured out the tropic Marin pro reef salt mixes to a DKH of 7.2 - something.

Long story short I used baking soda + RODI mix to experimentally raise my QT tank DKH. it’s PH is stable at 8.

I’m going to add a CO2 scrubber im the future when I buy a skimmer.

My first clownfish arrive this Thursday and are going to live in the QT for observation. Buying from dr. Reef.

Wow that’s crazy! Shows your instincts were correct.
Is it a new house with hyper efficient energy saving seals or something?