SPS tank's pH range

[skeety]

Which is a better daily pH swing for an SPS dominated tank:

8.0 in the AM .... 8.2 in the eve?

or

8.2 in the AM .... 8.4 in the eve?

[Geoff]

8.2 both night and day.

i do not think it really matters. if you are that specific with your pH than do 8.1 to 8.3.

G~

[tdwyatt]

Actually...


The lower the ambient seawater pH that a coral must work against to bring the pH of the calcioblastic endothelium high enough to precipitate out CaCO3, the more metabolically expensive it will be for the coral. I do not know if there is an absolute bottom pH at which hermatypic corals can no longer perform calcification, but I am sure that the lower the pH, the harder it is to precipitate out the CaCO3, and would speculate that there is a pH floor for skeletogenesis and Calcification.

As Geoff has already pointed out, a steady pH of 8.2 is most likely Ideal, if for no other reason than due to Darwinian selection that has culled out organisms over the eons that might be capable of these processes outside the range of pH's permitted by the bicarbonate/carbonate buffer system of seawater. I'd speculate that these life forms have developed/evolved around finding the right set chemical conditions in nutrient-poor waters, and that skeletogenesis is not the end (i.e., to produce a skeleton), rather that it is a means of improving the ability to attract CO2 or other anionic substances through the boundary layer via the generation of a proton (thought to be a byproduct, but may be the main metabolic goal of calcification, see T.A. McConnaughay's research on calcification generating a proton ca. 1996, Earth Sciences Review I think...)

Just as a matter of reference, using a properly adjusted CO2-based Ca reactor should keep your pH in the 8.0 to 8.2 range, but I have found that over time and tweaking, that the pH will stay between 8.10 and 8.28-8.30 until the gas supply drops off or the regulator becomes obstructed, at which point you'll start seeing higher pH every evening (up to as high as 8.5+), JME with the process. This usually coincides with sub 400 PPM Ca and dropping (sub 10 dKH) alkalinity in heavily populated hermatypic coral systems.


HTH

[skeety]

Okay...so MORE reinforcement to look into a Calcium reactor. heheh


Up until I got my MH lighting, my pH was a steady 8.2 (with Kalk dripping)

Since I've got my MH, I used to see swing from 8.0 am to 8.2 in the eve.

But I've upped the amound of Kalk I add to my top off from 1 tsp to 2tsp per gallon. Since then, I'm seeing a steady 8.15-8.2 in the morning and right before lights go out, I'm usually at 8.35-8.4. I'm guessing it's due to the increase in Kalk (makes sense). But I was just wondering if that's really bad...or just not optimal. Sounds like the later.

So it sounds like this is as good as it'll get until I switch to a Ca reactor, right?

[tdwyatt]

I don't think it will be an issue, corals are VERY adaptable (much tougher than we give them credit for), within this range it will not be a problem.

[Geoff]

Originally Posted by skeety

Okay...so MORE reinforcement to look into a Calcium reactor. heheh


Up until I got my MH lighting, my pH was a steady 8.2 (with Kalk dripping)

Since I've got my MH, I used to see swing from 8.0 am to 8.2 in the eve.

But I've upped the amound of Kalk I add to my top off from 1 tsp to 2tsp per gallon. Since then, I'm seeing a steady 8.15-8.2 in the morning and right before lights go out, I'm usually at 8.35-8.4. I'm guessing it's due to the increase in Kalk (makes sense). But I was just wondering if that's really bad...or just not optimal. Sounds like the later.

So it sounds like this is as good as it'll get until I switch to a Ca reactor, right?

this is prolly due to the increased growth of the corals, now that you have stronger lights.

G~

[drsyme]

Originally Posted by tdwyatt

Actually...


The lower the ambient seawater pH that a coral must work against to bring the pH of the calcioblastic endothelium high enough to precipitate out CaCO3, the more metabolically expensive it will be for the coral. I do not know if there is an absolute bottom pH at which hermatypic corals can no longer perform calcification, but I am sure that the lower the pH, the harder it is to precipitate out the CaCO3, and would speculate that there is a pH floor for skeletogenesis and Calcification.

hehe

Just when I thought I had heard everything Tom had to say, he says stuff like this.

[drsyme]

My new term for the week is "boundary layer."

[tdwyatt]

I'm just waiting to get my research stuff together to post on calcification and photosynthesis in the Think Tank once I finish the work on the TT project on algae and nutrient uptake issues (under the coralline algae thread)...