Growth rate vs. daily pH swing

karimwassef

karimwassef

Active member
I'm curious to collect data on the effect of daily pH variation (around a stable set point) on coral growth rate.

I'm starting with a near flat pH around 8.3 (0.02 intentional variation over 24hrs 8.28-8.32).

I'll take weakly measurements for 4 weeks. Then increase the variation and repeat.

Today is my first day. I've picked a coral and took the baseline pics
<a href="http://s1062.photobucket.com/user/karimwassef/media/1A6554EE-A66E-460F-9BAF-7680267EC6C3_zpsetme2cjg.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/1A6554EE-A66E-460F-9BAF-7680267EC6C3_zpsetme2cjg.jpg" border="0" alt=" photo 1A6554EE-A66E-460F-9BAF-7680267EC6C3_zpsetme2cjg.jpg"/></a>

Test zone
<a href="http://s1062.photobucket.com/user/karimwassef/media/0CDD2C6A-77C0-4C24-B5E0-9FEE365569C2_zpssz5vbboo.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0CDD2C6A-77C0-4C24-B5E0-9FEE365569C2_zpssz5vbboo.jpg" border="0" alt=" photo 0CDD2C6A-77C0-4C24-B5E0-9FEE365569C2_zpssz5vbboo.jpg"/></a>

Basic measures
<a href="http://s1062.photobucket.com/user/karimwassef/media/FA36A0C1-86EF-4C5C-B753-A4FE32FA998A_zpsbynzd5kx.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/FA36A0C1-86EF-4C5C-B753-A4FE32FA998A_zpsbynzd5kx.jpg" border="0" alt=" photo FA36A0C1-86EF-4C5C-B753-A4FE32FA998A_zpsbynzd5kx.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/F50F27D5-9AAA-44E9-B5FC-96C253672F75_zpsbvxl77tk.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/F50F27D5-9AAA-44E9-B5FC-96C253672F75_zpsbvxl77tk.jpg" border="0" alt=" photo F50F27D5-9AAA-44E9-B5FC-96C253672F75_zpsbvxl77tk.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/432AD00C-3660-441F-89B1-B0919BFE181E_zpspt0f86or.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/432AD00C-3660-441F-89B1-B0919BFE181E_zpspt0f86or.jpg" border="0" alt=" photo 432AD00C-3660-441F-89B1-B0919BFE181E_zpspt0f86or.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/3894CF81-286D-413A-A84C-5162A2D4767C_zpsvp8dibhp.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/3894CF81-286D-413A-A84C-5162A2D4767C_zpsvp8dibhp.jpg" border="0" alt=" photo 3894CF81-286D-413A-A84C-5162A2D4767C_zpsvp8dibhp.jpg"/></a>

Hopefully the pics are high res enough to use.

I'll measure pH, pH variance, temp, Alk, Ca, Mg and note all additives, feeding, or WCs.

Any advice? Anyone done something like this before?

Also looking for others who will do the same independently so we can compare results.
 
And salinity.

For temp, ph, and salinity : I'll capture min, max and ave for the week.

For Mg, Ca, and Alk : I'll take a snapshot on Saturday nights.
 
For reference - I inject outside air through my massive skimmer and my tank is in my garage so it's exposed to fresh air frequently.

Since we're talking pH, I want to make it clear that the tank has plenty of fresh air.

Next, I've dialed in to 8.3 because it's where my alkalinity is most stable with a slow gradual decline due to reef consumption vs. the kalk addition. It's also where I get little to no abiotic precipitation.

So once a week, I need to drip a little Alk additive for balance.

So no excess CO2 due to poor gas exchange + very stable alkalinity with this purposeful kalk drip aligned with a pH of 8.3.
 
Baseline (this week)-
Alk 9dKH
Ca 560ppm
Mg 1425ppm
pH 8.3 (8.26-8.34)
Salinity 30.0 (29.0-30.6)
Temp 81.0 (78.9-83.4)
 
I can tell you I saw a big change in grow from a a PH of 7.8-7.5 to 8.25-7.9 having my skimmer running (no skimmate)
 
Thanks. In your case, it looks like your average pH changed from 7.65 to 8.05 but your peak to peak swing was about the same ~ 0.3 (per day I assume?)

In my case, im actually trying to determine the opposite. I'm not looking at the effect of the base pH level (average over time), but the effect of peak to peak variation holding that center value of pH constant.

The first stage is nearly no swing around 8.3: peak to peak of 0.04 ~ 8.28-8.32 daily.

I'll then take the biggest step I'm willing to risk: peak to peak of 0.2 ~ 8.3-8.4 daily.

The third will be a forced inverse photo cycle: p2p of 0.2 but phased (I'll call it -0.2) = 8.4 at night and 8.3 by day.

I'll log Alk since I'm especially concerned about the third one...

Based on these three, I'll decide what to do next.
 
Here's my pH by the way. Two days ago, I changed from a static set point of 8.3 to a variable reference every 6 hours. The feedback loop tracks pretty well - with a +/- 0.2 error.

<a href="http://s1062.photobucket.com/user/karimwassef/media/5FD9BE28-0534-4D78-960A-D35377C3B038_zpsxyaygkpj.png.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/5FD9BE28-0534-4D78-960A-D35377C3B038_zpsxyaygkpj.png" border="0" alt=" photo 5FD9BE28-0534-4D78-960A-D35377C3B038_zpsxyaygkpj.png"/></a>
 
Nighttime growth filaments (2am)

<a href="http://s1062.photobucket.com/user/karimwassef/media/98FA1A4C-F901-4D15-A91B-844506A702CF_zpsroqfript.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/98FA1A4C-F901-4D15-A91B-844506A702CF_zpsroqfript.jpg" border="0" alt=" photo 98FA1A4C-F901-4D15-A91B-844506A702CF_zpsroqfript.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/93669184-D2A4-4CE0-B430-9E94DDC85644_zps8qfqzf1i.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/93669184-D2A4-4CE0-B430-9E94DDC85644_zps8qfqzf1i.jpg" border="0" alt=" photo 93669184-D2A4-4CE0-B430-9E94DDC85644_zps8qfqzf1i.jpg"/></a>
 
Tue: first feeding of the week
60ml phytoplex
60ml restor
0.5 tsp reef roids
0.5 tsp coral frenzy
0.5 tsp new life spectrum 1mm sinking pellet
1ml selcon
1 sally's frozen cyclops
1 argent frozen cyclopeeze
1 pemysis frozen mysis
 
 
I've read the articles on acidification. That's not the topic here.

It's about whether a daily variance (in the high pH range) is beneficial or harmful to coral growth.

So- it's not about 7.8 vs 8.2... It about whether a daily swing from 8.2 to 8.4 is better than a flat 8.3 all day.
 
To help a fellow Dallas area resident (we Texans have to stick together), the analogy would be physical exercise. Exercise forces the body to respond to physical stress by building stronger bones, stronger muscles, etc.

So, does pH variation do something similar with coral growth? Or does it do the opposite? Or neither? Are we better off (for growth) with reducing variation, or are we better off having some variation? Would a daily pH variation (at some yet-to-be-determined "ideal" range) increase coral growth? I would *think* (my opinion) that pH variation that closely matches what is on a natural reef would be what we would want to aim for. I personally like to level-out my daily pH swing (I get about 0.05 max swing per day), but I don't "chase" a particular pH value...and I let the mean value drift day-to-day...my dosing is entirely based on alkalinity needs.

An interesting article I just glanced through discusses pH swings:

High-Frequency Dynamics of Ocean pH: A Multi-Ecosystem Comparison
 
Last edited:
karimwassef, from the above study I found something of interest:

The pH recorded in coral reef ecosystems exhibited a distinct diel pattern characterized by relatively consistent, moderate fluctuations (0.1 < pH change < 0.25).
Click to expand...

So, I think for your experiments you might want to make your daily swings in the 0.1 to 0.25 range.
 
I was planning on a 0.2 peak to peak swing 8.2-8.4... Let's get that result and then see if we should grow the variance.
 
Upon further searching I found another article that I think applies to the objective of this thread:

Diel Variability in Seawater pH Relates to Calcification and Benthic Community Structure on Coral Reefs

From it:
Finally, our data suggest that as coral reef communities begin experiencing a greater daily duration of low pH values as a result of OA, the abundance of calcified organisms and the structural services they provide will likely be compromised in the foreseeable future.
Click to expand...
 
Last edited:
Hmmm...

I think this speaks to the strong coupling between the average pH and the variation. So, a 0.2 swing at 8.3 is very different from a 0.2 swing at 7.9. The variables are coupled, not independent.

If the swing drives pH into the OA range, I think the result becomes highly nonlinear.

I'm looking for a measure of the effect in the linear range - as far from the OA ranges as possible.

Great research! Thanks for digging in.
 
Tue: first feeding of the week
60ml phytoplex
60ml restor
0.5 tsp reef roids
0.5 tsp coral frenzy
0.5 tsp new life spectrum 1mm sinking pellet
1ml selcon
1 sally's frozen cyclops
1 argent frozen cyclopeeze
1 pemysis frozen mysis

Wed: second feeding of the week
1 tsp new life spectrum 1mm sinking pellet
3 tsp Ocean Nutrition Prime Reef Flakes
1ml selcon
1ml kent garlic Xtreme
1 pemysis frozen mysis

Thurs evening: third feeding of the week
1 tsp new life spectrum 1mm sinking pellet
1 tsp Kent Platinum ChromaXtreme medium sinking pellet
3 tsp Ocean Nutrition Prime Reef Flakes
1ml selcon
1ml kent garlic Xtreme
3 pemysis frozen mysis
1 argent frozen cyclopeeze
30ml Restor

Thurs after dark: fourth feeding of the week
60ml phytoplex
30ml restor
0.5 tsp reef roids
0.5 tsp coral frenzy
1 sally's frozen cyclops
1 argent frozen cyclopeeze
 
Here's this week's controlled pH variance. It was set to 8.3 average with 0.02 peak to peak = 8.28-8.32 with a known error of 0.02 so expecting 8.26-8.34 absolute min-max:

<a href="http://s1062.photobucket.com/user/karimwassef/media/12461193-E84B-426C-94B0-599E0F0DC125.png_zpsxt2k81yp.jpeg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/12461193-E84B-426C-94B0-599E0F0DC125.png_zpsxt2k81yp.jpeg" border="0" alt=" photo 12461193-E84B-426C-94B0-599E0F0DC125.png_zpsxt2k81yp.jpeg"/></a>

Pretty much as expected.
 
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