High pH - good for corals, bad for fish?

[DarthChaos]

How high, is too high - for pH?

Over the years I've read...the higher the pH the better. Heard rumors of some high end reefers pushing 9+ - doing a lot obviously to achieve this.

Now me, I'm currently pulling fresh air from my skimmer & dripping, 6mls of kalkwasser per minute (or adding little over 8.6L a day). Basically got my kalk replacing evaporation, at this point. This is giving my a nice pH boost. Corals - doing fantastic, never seen better coral growth!

Alk - Calc and Mag generally run elevated - dosing minimal, due to amount kalkwasser. Don't need to dose as much 2 part.

BUT, I started thinking....is running elevated pH in a reef tank, a bad thing? I mean - the higher the pH, the more alkaline the water, no?

Right now I'm fallow (velvet outbreak) - but restocking in a few weeks. Now - when I did have fish, they were all happy, healthy and fat (well - till I got velvet). But I'm just curious....if the elevated pH - will cause me issues, moving fwd?

Some readings indicated high pH = stress and what not...but doesn't talk about HOW high of pH.

Thoughts? Or am I just overthinking...

 

[Spare time]

I wouldn't worry about the pH level you have. I assume you know the error range of that meter? As for those going 9+, I think that is insane and I don't know how that was even possible outside of testing errors or massive overdoses of a pH boosting substance.

 

[DarthChaos]

I wouldn't worry about the pH level you have. I assume you know the error range of that meter? As for those going 9+, I think that is insane and I don't know how that was even possible outside of testing errors or massive overdoses of a pH boosting substance.

Ya, I run a calibration every 3 months - just to make sure it's working....since it's the only thing I'm relying on to monitor pH.

So far, hasn't given me a reason to suspect it's accuracy

 

[Troylee]

I wouldn't worry about the pH level you have. I assume you know the error range of that meter? As for those going 9+, I think that is insane and I don't know how that was even possible outside of testing errors or massive overdoses of a pH boosting substance.

My thoughts exactly as you’d have precipitation going on and a snowy tank lol.

 

[GARRIGA]

Doesn’t calcium start to precipitate at 8.55 therefore pushing 9 means what. Constantly dosing and testing calcium or at that point it precipitates quicker than consumed/utilized? Never doing this but first I hear of 9 and now curiosity bit me.

 

[DarthChaos]

Doesn’t calcium start to precipitate at 8.55 therefore pushing 9 means what. Constantly dosing and testing calcium or at that point it precipitates quicker than consumed/utilized? Never doing this but first I hear of 9 and now curiosity bit me.

I've hit almost 8.7 (again, IF we trust the Apex probe) and never had an issue. In fact - currently, I'm not even dosing Calcium.. I haven't needed too in months. The kalkwasser is replacing what I'd normally be dosing.

I mean - if I REALLY wanted to, adding a Co2 scrubber and an airstone, I'm quite confident I could get my pH upwards of 9. Now - I'm just lazy, cheap and really don't wanna run experiments on "my" reef system! Lol

I mean - if higher pH does = better, faster growth...then it makes sense to chase the pH dragon and see where it takes you, no?

 

[Randy Holmes-Farley]

I’ve not seen evidence of organism problems at high except certain types of macroalgae that do not like the reduced availability of CO2.

I do not think it likely that pH 9 is sustainable in a reef tank.

 

[GARRIGA]

I’ve not seen evidence of organism problems at high except certain types of macroalgae that do not like the reduced availability of CO2.

I do not think it likely that pH 9 is sustainable in a reef tank.

How does one counter the calcium precipitation? Dose more calcium which wouldn't that require constant testing and filter floss the precipitate?

 

[DarthChaos]

I’ve not seen evidence of organism problems at high except certain types of macroalgae that do not like the reduced availability of CO2.

I do not think it likely that pH 9 is sustainable in a reef tank.

Perfect! I shall carry on without stressing it then.

 

[Randy Holmes-Farley]

How does one counter the calcium precipitation? Dose more calcium which wouldn't that require constant testing and filter floss the precipitate?

Accelerated consumption of alkalinity and calcium is an attribute of higher pH, and the higher you want to keep it the more it accelerates.

 

[GARRIGA]

I’ve not seen evidence of organism problems at high except certain types of macroalgae that do not like the reduced availability of CO2.

I do not think it likely that pH 9 is sustainable in a reef tank.

Wouldn't the reduce availability of co2 also affect coral photosynthesis especially since increased pH raises consumptionm? At some point likely detrimental even if one could sustain 9 plus.

 

[Troylee]

I’m pretty sure those higher ph levels are detrimental to fish! I’ve never tested it nor do I care to try.. maybe @Jay Hemdal can chime in? I believe it burns their gills and stresses their immune systems when we get over 8.5 or something along those lines.

 

[Randy Holmes-Farley]

Wouldn't the reduce availability of co2 also affect coral photosynthesis especially since increased pH raises consumptionm? At some point likely detrimental even if one could sustain 9 plus.

Many marine organisms, which I believe includes most corals, get CO2 from bicarbonate, not from CO2 itself, and bicarbonate doesn't greatly drop with smallish pH changes.

I discuss that here:

Photosynthesis and the Reef Aquarium, Part I: Carbon Sources by Randy Holmes-Farley - Reefkeeping.com

there are many pertinent sections, but this talks about the macroalgae comment I made:

Photosynthesis of Macroalgae as a Function of pH

---

One of the side effects of the necessity of taking up carbon dioxide to photosynthesize is that pH may affect the rate of photosynthesis, because the amount of carbon dioxide (as CO2 or H2CO3) in the water varies with pH. Assuming constant carbonate alkalinity, the effect is quite strong. A drop of 0.3 pH units implies a doubling of the carbon dioxide concentration. A reef aquarium at pH 8.5, for example, has one fourth the carbon dioxide of a reef aquarium at pH 7.9, assuming the carbonate alkalinity is the same.

Aquarists may rightly wonder whether organisms are able to photosynthesize efficiently as the pH is raised. The answer is mixed. Some can and some cannot. Those organisms that rely solely on carbon dioxide may not. Those that rely on both carbon dioxide and bicarbonate have a better chance of retaining efficiency at higher pH because a much larger amount of bicarbonate is present, and it does not change as rapidly with pH over the range of interest to aquarists.

Table 1 shows the response of a variety of macroalgae in terms of their ability to photosynthesize at pH 8.1 and 8.7. In seawater with constant carbonate alkalinity, there is 20% as much carbon dioxide at pH 8.7 as at pH 8.1, so an organism relying on carbon dioxide alone might experience a large drop in photosynthetic rate over this range. Clearly, the response varies with species. Chaetomorpha aerea, in particular, may be of substantial interest to aquarists. It is not necessarily the exact species that many grow in refugia (which is unidentified as far as I can tell), but this species of Chaetomorpha shows a 25% drop in photosynthesis when exposed to the higher pH. That drop is not as large as some other species, but may still be important, and it is more than many other species of macroalgae.

Of course, the photosynthesis rate does not necessarily translate to growth rates. If other nutrients are limiting growth (nitrogen, phosphorus, iron, etc.), then it may not matter if the rate of photosynthesis is reduced at higher pH. But because these nutrients are often present in surplus in reef aquaria, it may well be that carbon uptake is limiting in some cases, and in those cases aquarists might benefit from ensuring that the pH is not too high.

 

[GARRIGA]

Many marine organisms, which I believe includes most corals, get CO2 from bicarbonate, not from CO2 itself, and bicarbonate doesn't greatly drop with smallish pH changes.

I discuss that here:

Photosynthesis and the Reef Aquarium, Part I: Carbon Sources by Randy Holmes-Farley - Reefkeeping.com

there are many pertinent sections, but this talks about the macroalgae comment I made:

Photosynthesis of Macroalgae as a Function of pH

---

One of the side effects of the necessity of taking up carbon dioxide to photosynthesize is that pH may affect the rate of photosynthesis, because the amount of carbon dioxide (as CO2 or H2CO3) in the water varies with pH. Assuming constant carbonate alkalinity, the effect is quite strong. A drop of 0.3 pH units implies a doubling of the carbon dioxide concentration. A reef aquarium at pH 8.5, for example, has one fourth the carbon dioxide of a reef aquarium at pH 7.9, assuming the carbonate alkalinity is the same.

Aquarists may rightly wonder whether organisms are able to photosynthesize efficiently as the pH is raised. The answer is mixed. Some can and some cannot. Those organisms that rely solely on carbon dioxide may not. Those that rely on both carbon dioxide and bicarbonate have a better chance of retaining efficiency at higher pH because a much larger amount of bicarbonate is present, and it does not change as rapidly with pH over the range of interest to aquarists.

Table 1 shows the response of a variety of macroalgae in terms of their ability to photosynthesize at pH 8.1 and 8.7. In seawater with constant carbonate alkalinity, there is 20% as much carbon dioxide at pH 8.7 as at pH 8.1, so an organism relying on carbon dioxide alone might experience a large drop in photosynthetic rate over this range. Clearly, the response varies with species. Chaetomorpha aerea, in particular, may be of substantial interest to aquarists. It is not necessarily the exact species that many grow in refugia (which is unidentified as far as I can tell), but this species of Chaetomorpha shows a 25% drop in photosynthesis when exposed to the higher pH. That drop is not as large as some other species, but may still be important, and it is more than many other species of macroalgae.

Of course, the photosynthesis rate does not necessarily translate to growth rates. If other nutrients are limiting growth (nitrogen, phosphorus, iron, etc.), then it may not matter if the rate of photosynthesis is reduced at higher pH. But because these nutrients are often present in surplus in reef aquaria, it may well be that carbon uptake is limiting in some cases, and in those cases aquarists might benefit from ensuring that the pH is not too high.

That makes sense but my own experience with plants in FW absent fish to add co2 resulted in alkalinity dropping near zero and pH becoming unstable. Even with the high co2 levels in my house the plants were apparently stripping the available co2 in the water which was fixed once a heavy load of fish added.

Found the cause to effect from researching planted aquariums where co2 is added. Latter I knew since the 70s yet the affect on alkalinity was new. Therefore, isn't the use of bicarbonate in photosynthetic organism not related to first exhaustion of available co2? Perhaps I'm not comprehending the section provided.

 

[Randy Holmes-Farley]

That makes sense but my own experience with plants in FW absent fish to add co2 resulted in alkalinity dropping near zero and pH becoming unstable. Even with the high co2 levels in my house the plants were apparently stripping the available co2 in the water which was fixed once a heavy load of fish added.

Found the cause to effect from researching planted aquariums where co2 is added. Latter I knew since the 70s yet the affect on alkalinity was new. Therefore, isn't the use of bicarbonate in photosynthetic organism not related to first exhaustion of available co2? Perhaps I'm not comprehending the section provided.

Organisms that use bicarbonate for CO2 do not actually consume alkalinity. They convert the bicarbonate to CO2 and spit out OH-, maintaining the alkalinity in the water:

 

[GARRIGA]

Organisms that use bicarbonate for CO2 do not actually consume alkalinity. They convert the bicarbonate to CO2 and spit out OH-, maintaining the alkalinity in the water:

I'm simplifying it. I know they don't consume alkalinity. Point being I thought they take bicarbonates only in the absence of co2.

 

[Randy Holmes-Farley]

I'm simplifying it. I know they don't consume alkalinity. Point being I thought they take bicarbonates only in the absence of co2.

Different organisms do different things, but some clearly do not take CO2 directly, which is why they continue to thrive even as pH rises.

 

[Jay Hemdal]

I’m pretty sure those higher ph levels are detrimental to fish! I’ve never tested it nor do I care to try.. maybe @Jay Hemdal can chime in? I believe it burns their gills and stresses their immune systems when we get over 8.5 or something along those lines.

Sorry - I don't have any experience keeping marine fish at a pH above 8.4

With pH probes, my mantra is: when in doubt, try a secondary test method and ensure your triple point standardization is done properly and frequently enough.

 

[Dom]

I’m pretty sure those higher ph levels are detrimental to fish! I’ve never tested it nor do I care to try.. maybe @Jay Hemdal can chime in? I believe it burns their gills and stresses their immune systems when we get over 8.5 or something along those lines.

Now I would think just the opposite.

As I understand it, a higher pH number means less acidic water. Lower pH numbers mean water which is more acidic. I would think gill burn would be more of an issue on the low pH end of the scale.

 

[Troylee]

Now I would think just the opposite.

As I understand it, a higher pH number means less acidic water. Lower pH numbers mean water which is more acidic. I would think gill burn would be more of an issue on the low pH end of the scale.

Yeah I’m not exactly sure… that’s why I was asking Jay if he had any intel.. I know I’ve read it, in a few places. I did a quick google search and aquaforest had this to say.. if it’s true or not I have no clue. But I have heard it a few times or better yet I should say read it! They don’t clarify what’s high thou lol..