Kalk Reactor for pH control
- Thread starter t.trezona
- Start date
disc1
-RT * ln(k)
I think so.
disc1
-RT * ln(k)
Yes, when you are talking about intracellular pH, but remember all these organisms are running a significant proton gradient. So you would have to lower the extracellular pH to something well below 7 before you mess with the intracellular. HighlandReefer put up a good article on intracellular pH in stony corals not long ago I'll see if I can find it.
0.3pH points represents a doubling of the amount of hydroxide in the water. I don't think doubling is a very big thing, especially when the intracellular pH of the coral is something like 100x lower. We're talking about a hydroxide concentration of 10^-6 M. I don't see much difference between 1* 10^-6 and 2* 10^-6 or even 4* 10^-6M. That is such a tiny tiny amount, and I am positive that your average coral on the reef, between weather and everything else is well adapted to seeing pH changes of that magnitude. If we were out on the ends of the pH scale, like at 2 or 10, then I could see it being a huge difference, but this close to 7 it's just not.
As an analogy, coral like their temps to be stable too right? But we don't stress out over a few tenths of a degree or even a whole degree swing because it isn't that much. We still call that stable. But with pH we are suddenly thinking that a change of 1* 10^-6M hydroxide is going to have some huge effect? I just don't see it. I don't think anything in the world is that sensitive to pH. Just like I don't think any living creature is sensitive to a 0.1F temp change.
Remember that not only is the scale for pH logarithmic, but so are most of the effects. That's why we made the scale logarithmic. The particular chemical reactions we are worried about, like ATPsynthase, are going to work over a range of pH values that varies over a pretty big range. So long as the organism can maintain a proton gradient that gradient doesn't need to be huge. All you really need is for it to be downhill.
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disc1
-RT * ln(k)
Yes, much larger diurinal swings than that occur on reefs.7.9 as al ow is ok,imo. I do prefer it higher though.
As for kalk dosing, FWIW, I modeled my 24/7 approach on the still reservoir Randy outlines in his articles. Mine is a 32 gallon brute can with a lid. Fill and refill entails: shutting the dosing pump off; filling it with ro/di water; stirring in new kalk with a length of pvc pipe ;letting it settle for two hours ;and turning the pump back on.
I also dose a little baked baking soda at this point to make up for the down time. I don't need to dose any extra calcium because I do regular water changes with a high calcium salt. This routine meets the needs for calcium and alkalinity in my system which is loaded with growing sps and has for over 3yrs.
,I use the liter meter 3 perstaltic pump which has a built in timer. I set it to dose a specific number of liters for 24hours. The timer regulates the dose ,so that an equal 1/150th increment is dosed every 9.6 minutes . The inlet tube is kept a few inches of the bottom to avoid sucking up undissolved calcium hydroxide or impurities. Only clear fully saturated limewaer is dosed.
Any good peristaltic pump and timer set up can work well. Diaphram pumps and timers are another option.
To maintain 8.15 to 8.30 ph , my system which is dosed with organic carbon ,despite plenty of surface agitation and 24/7 kalk dosing for all top off , still requires a little boost( and gets a bump of about .15 ph) from a CO2 scrubber linked to the skimmer air intakes .
Tom
I've always thought dosing Kalk via water top off was a little backward. During the day when photosynthesis is going on obviously the pH is higher due to CO2 extraction from the water. When the lights are on and the water surface is the warmest there is more evaporative water loss. The Kalk flow is therefore greatest during the day, which drives your pH up even higher, making the overall swings greater. Why not limit the evaporative water replacement to night time only?
I've always thought dosing Kalk via water top off was a little backward. During the day when photosynthesis is going on obviously the pH is higher due to CO2 extraction from the water. When the lights are on and the water surface is the warmest there is more evaporative water loss. The Kalk flow is therefore greatest during the day, which drives your pH up even higher, making the overall swings greater. Why not limit the evaporative water replacement to night time only?
Many folks dose their limewater only at night, but I choose to replace evaporated water with limewater 24/7. Putting it on a timer might work, but it is one more thing among many that might fail when I'm away on vacation.
Why not limit the evaporative water replacement to night time only?
Because I favor a 24 hour constancy in calcium and alk levels as well as specific gravity over managing diurnal ph swings . I've dosed it only at night in the past and it's ok but I prefer 24/7.
Because I favor a 24 hour constancy in calcium and alk levels as well as specific gravity over managing diurnal ph swings . I've dosed it only at night in the past and it's ok but I prefer 24/7.
My system is completely enclosed within a wall. I have huge air movement in and out of the space over the water surface so I get quite a lot of evaporation. Controlling my Kalk reactor with pH just matches evaporative losses. If I changed my system so that the Kalk dripped continuously the volume added would be about the same.
Thank you all for your input on this. I love this chemistry forum. It's where the really bright people hang out. Brings back a lot of memories too. I took a chemistry course every semester of every year in college and grad school so I actually get most of what Randy and you other chemistry guys have to say. A decent understanding of chemistry is really helpful for putting together a successful reef system. I know there are a lot of really stupid questions on these forum pages, but you guys have amazing patients and grace with your answers. I appreciate that. Merry Christmas.
Tom, Merry Christmas to you too.
Controlling my Kalk reactor with pH just matches evaporative losses. If I changed my system so that the Kalk dripped continuously the volume added would be about the same.
It should be the same amount of total limewater. in a 24 hour period. However,obviously it will not be evenly distributed over 24 hours. There will stretches of time without any additions of fresh water or calcium or CO3 during ongoing precipitation and evaporation. It's a tradeoff to dose limewater only at night to manage diurnal swings: constancy in alk , calcium and sg vs flattening or eliminating a ph swing.
Controlling my Kalk reactor with pH just matches evaporative losses. If I changed my system so that the Kalk dripped continuously the volume added would be about the same.
It should be the same amount of total limewater. in a 24 hour period. However,obviously it will not be evenly distributed over 24 hours. There will stretches of time without any additions of fresh water or calcium or CO3 during ongoing precipitation and evaporation. It's a tradeoff to dose limewater only at night to manage diurnal swings: constancy in alk , calcium and sg vs flattening or eliminating a ph swing.
Not much beyond episodic changes say do to heavy rains , for the elements or specific gravity given given the vastness of the sea and miscibility of the elements except for locations near esturarial run offs as far as I know. But there must be a study or two out there .
Diurnal ph swings in some cases are surprisingly large:
http://pages-142.unibe.ch/science/paloa/talks/Catalina_Carles_SN.pdf
This from it for example:
Summary (non-exhaustive) of instrumental reef pH
variability
Reef Timescale
pH range
and ΔpH
Reference
Molokai Reef, Hawaii, US diurnal 7.8 – 8.4
0.6 units
Yates and Halley, 2006,
Biogeosciences
Rukan-sho Reef,
Okinawa, Japan
diurnal 7.9 – 8.7
0.8 units
Ohde and van Woesik, 1999,
Bull. Mar. Sci.
Shiraho Reef, Ryukyu
Islands, Japan
diurnal 7.8 – 8.8
1 unit
Suzuki et al., 1995,
Sediment. Geol.
Enewetak atoll diurnal 0.1 – 0.2
units
Schmalz and Swanson, 1969,
J. Sediment. Petrol.
Hog Reef, Bermuda annual 7.9 – 8.1
0.2 units
Bates et al., submitted,
Biogeosciences
Remember Tom . I said its a tradeoff; it may not be a very big one either way. You aked me why I didn't dose limewater only at night . My answer was that I favor the opposite side of the trade ,ie stable alk alcium and sg vs a flatter ph swing which btw can be managed in alternative ways if it's a major concern.
Diurnal ph swings in some cases are surprisingly large:
http://pages-142.unibe.ch/science/paloa/talks/Catalina_Carles_SN.pdf
This from it for example:
Summary (non-exhaustive) of instrumental reef pH
variability
Reef Timescale
pH range
and ΔpH
Reference
Molokai Reef, Hawaii, US diurnal 7.8 – 8.4
0.6 units
Yates and Halley, 2006,
Biogeosciences
Rukan-sho Reef,
Okinawa, Japan
diurnal 7.9 – 8.7
0.8 units
Ohde and van Woesik, 1999,
Bull. Mar. Sci.
Shiraho Reef, Ryukyu
Islands, Japan
diurnal 7.8 – 8.8
1 unit
Suzuki et al., 1995,
Sediment. Geol.
Enewetak atoll diurnal 0.1 – 0.2
units
Schmalz and Swanson, 1969,
J. Sediment. Petrol.
Hog Reef, Bermuda annual 7.9 – 8.1
0.2 units
Bates et al., submitted,
Biogeosciences
Remember Tom . I said its a tradeoff; it may not be a very big one either way. You aked me why I didn't dose limewater only at night . My answer was that I favor the opposite side of the trade ,ie stable alk alcium and sg vs a flatter ph swing which btw can be managed in alternative ways if it's a major concern.
