Does alkalinity vary throughout the day?

[Randy Holmes-Farley Verified Community Expert]

What more proof do we need to say that lights or ph have direct effect on alk consumption, whitch is usually our corals on our tanks?

I don’t know. Who are you trying to convince? I’ve said this exact thing for years, and never once disagreed with it in this thread or any other. :)

 

[Reefering1]

Imo, it ask about the lights. Light drives photosynthesis, in turn raising ph and consumption. No light= no consumption, right?

 

[Garf]

It also gets more confusing when the coral/algae relationship is able to produce internal pH of 8.5, even if the pH of the bulk water is 8.1.

 

[Randy Holmes-Farley Verified Community Expert]

Imo, it ask about the lights. Light drives photosynthesis, in turn raising ph and consumption. No light= no consumption, right?

The issue is, what if the pH is lower during the day, say, with a big reverse lit refugium. Is alk demand then higher when corals are getting light, or higher when corals are in higher pH.

There are plausible mechanisms for both to be true.

 

[Reefering1]

The issue is, what if the pH is lower during the day, say, with a big reverse lit refugium. Is alk demand then higher when corals are getting light, or higher when corals are in higher pH.

There are plausible mechanisms for both to be true.

I would think that there is "no chance" of a coral consuming more in the dark, regardless how high the ph, than during peak photosynthesis...

 

[Randy Holmes-Farley Verified Community Expert]

I would think that there is "no chance" of a coral consuming more in the dark, regardless how high the ph, than during peak photosynthesis...

Why do you think that? I’ve never seen any data to distinguish the direct light from the pH effect.

 

[AlexandraDreadlocksPanda]

Alkalinity consumption varies massively throughout the photoperiod, so if you are supplementing Alkalinity at a constant rate over 24 hours it will rise and fall dramatically. When I first started using my Alkatronic, my calcium reactor was giving me Alk swings of nearly 1 DKH over a 24 hour period. Now switched to dosing Randy’s 2 part with a DoseTronic, and it’s still busy tweaking doses to iron out peaks and troughs, but essentially about 90% of my Alk consumption occurs from about an hour after lights on to an hour after they go off… I’m assuming that the Photosynthesis needs a certain threshold level of light to start the reaction, then it doesn’t just stop as soon as light go off…

 

[Reefering1]

Why do you think that? I’ve never seen any data to distinguish the direct light from the pH effect.

I have no real data to support my thoughts and assumptions, I'm proposing the question more than anything..
BUT...
I have monitored my alk hourly, consumption was definitely significantly highest within a hour or 2 of peak lighting. Then ph climbs.. I assume by photosynthesis of corals/ algea consuming c02. Then slows as lights ramp down, ph soon follows. Are you suggesting corals will consume more in the dark, because of high ph, than in peak photosynthesis? If not to grow, why else do the corals need light? Consumption=growth, correct? (Excluding precipitation)

 

[Randy Holmes-Farley Verified Community Expert]

I have no real data to support my thoughts and assumptions, I'm proposing the question more than anything..
BUT...
I have monitored my alk hourly, consumption was definitely significantly highest within a hour or 2 of peak lighting. Then ph climbs.. I assume by photosynthesis of corals/ algea consuming c02. Then slows as lights ramp down, ph soon follows. Are you suggesting corals will consume more in the dark, because of high ph, than in the dark? If not to grow, why else do the corals need light? Consumption=growth, correct? (Excluding precipitation)

This is a complicated topic with plausible and clear reasons why corals calcify faster in both light and in higher external pH.

Alk is consumed in skeletal deposition, not by photosynthesis, and neither formation of tissue nor growth of tissue consumes alkalinity.

 

[Miami Reef]

Would the test be as simple as raising the alk to 9dKH (starting at 8dKH) with hydroxide before the lights shut off, then measure the consumption over the evening.

Then raise the alk back to 9dKH with bicarbonate and inject CO2 during the day and measure that alk consumption?

Could that work?

 

[Pod_01]

If not to grow, why else do the corals need light?

There are NPS (non photosynthetic corals) so perhaps the light is not the key to Alk consumption.

I never had any NPS corals but they do sound interesting.

 

[Randy Holmes-Farley Verified Community Expert]

Would the test be as simple as raising the alk to 9dKH (starting at 8dKH) with hydroxide before the lights shut off, then measure the consumption over the evening.

Then raise the alk back to 9dKH with bicarbonate and inject CO2 during the day and measure that alk consumption?

Could that work?

As long as pH can be maintained higher at night, it could work. But I think it needs to be done long enough to be stable. Alk and pH changes may disrupt corals.

 

[Reefering1]

This is a complicated topic with plausible and clear reasons why corals calcify faster in both light and in higher external pH.

Alk is consumed in skeletal deposition, not by photosynthesis, and neither formation of tissue nor growth of tissue consumes alkalinity.

Right. But isn't the tissue(animal) facilitating the skeletal deposition? Ie dead corals don't grow.
Can you suggest relevant reading? so I can come back with more informed questions..

 

[Miami Reef]

Right. But isn't the tissue(animal) facilitating the skeletal deposition? Ie dead corals don't grow.

I was thinking that, too.

 

[Reefering1]

There are NPS (non photosynthetic corals) so perhaps the light is not the key to Alk consumption.

I never had any NPS corals but they do sound interesting.

I didn't consider nps. Good point.
I loved my volley ball size dendro of the past.

 

[Reefering1]

As long as pH can be maintained higher at night, it could work. But I think it needs to be done long enough to be stable. Alk and pH changes may disrupt corals.

So maybe, maintain alkalinity and inject c02 to supress ph?

 

[Miami Reef]

@Randy Holmes-Farley Do you think some acropora cannot tolerate alkalinity at 10dKH? Some of mine are really happy, but others could be better. Nutrients are detectable and high enough, but not too high.

I’m trying to rule out any culprits, and alkalinity is the last thing on my list. I always preferred to keep my alk higher. Do you think alk around 10dKH is universally safe for acros as long as it’s kept stable?

Do you think I can rule alk out as a culprit for why some of my acros aren’t doing too well? Or do I need to experiment with lower levels to find out?

 

[Randy Holmes-Farley Verified Community Expert]

Right. But isn't the tissue(animal) facilitating the skeletal deposition? Ie dead corals don't grow.
Can you suggest relevant reading? so I can come back with more informed questions..

It is clear from many studies, both scientific and BRS, that calcification increases as external pH rises. That may be due to ease of secreting the H+ formed by converting bicarbonate to carbonate.

Photosynthesis also increases internal pH which can boost calcification.

I didn’t search around much, but here’s an article that looks at the issue:

https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2015.00122/full

 

[Randy Holmes-Farley Verified Community Expert]

So maybe, maintain alkalinity and inject c02 to supress ph?

That would work.

 

[Randy Holmes-Farley Verified Community Expert]

@Randy Holmes-Farley Do you think some acropora cannot tolerate alkalinity at 10dKH? Some of mine are really happy, but others could be better. Nutrients are detectable and high enough, but not too high.

I’m trying to rule out any culprits, and alkalinity is the last thing on my list. I always preferred to keep my alk higher. Do you think alk around 10dKH is universally safe for acros as long as it’s kept stable?

Do you think I can rule alk out as a culprit for why some of my acros aren’t doing too well? Or do I need to experiment with lower levels to find out?

I really don’t know if high alk may be all or part of the issue.