Is it PH or ALK stability for the win?

[IPT]

I know, or I should say "my understanding of the following is",

ALK and Ph have an intimate relationship where one affects the other.
SPS tend to calcify (grow) at higher PH's. (mid 8's)
SPS also tend to Calcify (grow) at higher ALK levels (say Dkh off 11 vs 8)
Most (if not all?) growth occurs during the day.
SPS LOVE stability!

I'm happy to and generally run my tank Alk between 8.4 and 8.8. Leaves me some buffer and room for error. I have a well ventilated area and I dose KALK to maximize my Ph potential.

What is throwing me for a loop, is all this hub-bub about dosing KALK all at night to keep an elevated Ph throughout the night (where it normally would drop without the photosynthesis and C02 consumption). There has been quite a few people raving about the positive effects of doing this. I can understand the concept of chasing stability here, but if you dose most if not all of your Kalk at night to keep the Ph up, then I would imagine you'd see an upward swing in Alk (no consumption of it overnight) and then a drop during the day because not only is it being consumed, you're no longer dosing during those hours either.

So, is there any merit to this method? Keeping Ph more stable, (in effect elevating it at night to combat the normal night time fall) in exchange for swings in the Alk?

 

[Mr. Mojo Rising]

I haven't measured ph in years.... I test alk very frequently, nightly or else every other night. To me, alk is the most important.

 

[CHSUB]

Most (if not all?) growth occurs during the day

I’m not sure this is true, however your point and thoughts are excellent. I elevate ph at night with kalk, doing so since the 90’s, because it is just what I do. Maybe you point out a better way? I’ve read 7.7 and lower ph is bad and can slowly dissolve calcium carbonate, maybe the number is actually lower? Hopefully there’s data available that can support your hypothesis, besides hobby observation. It would be difficult from me to change dosing to day time, because it goes against a successful practice that I have used for decades.

 

[p1u5h13r4m24]

I know a lot of sps guys who don’t chase ph. I don’t dose kalk at night I just dose it in the morning right before lights turn on. This will boost my ph closer to 8 right before it’s time to grow.
As others said dkh is the main thing to keep stable. I keep dkh 7.5-8.0 say I change it to 8.5 over the course of next wee my corals will be mad for a few days because they are used to 7.5-8.0. I’ve had larger swings and slowly came back down. As long as everything else is right it shouldn’t be an issue.
Lastly if my ph is in the 7.7 range
I will dose more kalk to try to bump it up. For example I wake up at 4 am an ph is 7.7 I’ll dose 200ml of kalk. Only about a .1 dkh increase for me and ph will bump up to about 7.85.

 

[Randy Holmes-Farley Verified Community Expert]

There is a complex interplay between pH, alk, and the concentrations of things corals can actually care about, which does not literally include alkalinity. Those might be bicarbonate, carbonate and pH.

As with most things chemical, you run into huge complexities that reefers often overlook (and rightly so unless the chemistry details interest them) when you look deeply into the issues.

For example, unless pH is stable, stable alkalinity does not mean stable bicarbonate or carbonate.

Consequently, while stable alk may (but also may not) empirically show corals are happiest, it seems that coming up with an explanation why is quite elusive.

I’ll also note that stability means different things. A range of alk the same every day is very different than a stable alk that suddenly changes one day, and there are good explanations for that.

Fauna Marin has been pushing a once a day alk dose plan that seems to work well for users. It is obvious that those tanks have less alk stability within a given day than those dosed automatically by a controller.

I discuss this whole conundrum here:
https://www.reef2reef.com/threads/alkalinity-stability-ph-stability-are-they-even-different.711768/

 

[CHSUB]

There is a complex interplay between pH, alk, and the concentrations of things corals can actually care about, which does not literally include alkalinity. Those might be bicarbonate, carbonate and pH.

As with most things chemical, you run into huge complexities that reefers often overlook (and rightly so unless the chemistry details interest them) when you look deeply into the issues.

For example, unless pH is stable, stable alkalinity does not mean stable bicarbonate or carbonate.

Consequently, while stable alk may (but also may not) empirically show corals are happiest, it seems that coming up with an explanation why is quite elusive.

I’ll also note that stability means different things. A range of alk the same every day is very different than a stable alk that suddenly changes one day, and there are good explanations for that.

Fauna Marin has been pushing a once a day alk dose plan that seems to work well for users. It is obvious that those tanks have less alk stability within a given day than those dosed automatically by a controller.

I discuss this whole conundrum here:
https://www.reef2reef.com/threads/alkalinity-stability-ph-stability-are-they-even-different.711768/

Thanks. Very complicated for non-scientists and not sure hobbyist have much to gain trying to understand the details you provided. I tried, but not sure I fully grasp the complexity. However, I believe I’m doing it the “right way”; maintaining the highest pH possible when the value is at its lowest, nighttime kalk dosing.

After reading, feel “smarter”….haha!

 

[IPT]

I think it is more complex than we (hobbyists) think (as Randy points out). I look forward to reading the link he provided later.

From my quick glace at the posts maybe the higher night time Ph makes bicarbonate (or other thing) more available, allowing for better growth? Knowing there is a swing of Alk with specific dosing times (at night per say) done consistently and without an extreme Alk swing may also in fact be creating a stable environment none the less.

Seems like many thing we may see the effects long before we can understand it. It does appear, albeit anecdotally, there is a notable value in having the Ph more elevated (or at least not dropping as much) during the evening hours.

 

[exnisstech]

I’ve read 7.7 and lower ph is bad and can slowly dissolve calcium carbonate, maybe the number is actually lower?

It must be lower.
All of my tanks run the same when tested but I monitor my acro tank. My pH is 7.6 with a peak of 7.8 and corals are doing well IMO. I can get a peak of 8.1 when the house is open in warmer weather. TBO I never really cared about pH. I guess I still don't and just started monitoring out of curiosity. I'm far from an expert but what I've gathered from reading is that high pH can accelerate growth but doesn't do much more, at least from what I've read. My alk runs mid 8s dkH.

 

[BryanM]

My mindset for this is that ph naturally fluctuates day and night.

Therefore I focus on alk stability, and while I have a PH probe and monitor it, I'm really only concerned if I see a big change from normal. Though lately my ph is also pretty stable IMO, 8-8.1.

 

[mook1178]

Alkalinity and CO2 concentration are the major controllers of pH. I didn't bother with pH, have never measured it. Keep alkalinity and CO2 in check, pH will follow

 

[Ziggy17]

When I stopped caring about daytime PH swings and focused on alk stability, my sps started to like me way more. TBH, my LPS and zoas didn’t seem to care either way. They have for the most part, always happy (ish).

Daily Alk range if 8.9-9.1
Daily PH range 8- 8.4

 

[Ishy]

We manage to keep Alk and pH pretty stable. Can only be a good thing imo.