Dosing CO2??

[Boomer]

3-D

First what are your water parameters, i.e., Ca++, Mg++ Alk, and pH. The stuff on the glass "sounds" like abiotic precipitation.

And yes, a normal NSW pH of 8.2 - 8.4 is better as is a slightly elevated Alk , as long as the Alk is not to high.

One issue on the glass makes me think your Mg++ is to low and is causing deposits of calcite. Do you have this stuff on pumps also. And lastly, what is the temp deferential between the inside tank glass and the outside tank glass, farthest from the light and closest to the light, as this makes me think it is a heat issue creating the deposits. The warmer glass at the glass water interface can cause abiotic precip, just like you see at the water/ heater or water/pimp interface, which have higher temps. As temp increases precip of calcite increases.

Adding CO2 will not help this, as it will lower the pH where you do not want to be. Pick a pH I don t' care which. If you have a tank with a pH of 8.3 and some else has a tank with a pH of 8.3 the % of CO2:HCO3:CO3 will be the same. The only difference will be the amount of them, a function of Alk. And to high a pH and Alk and especially at elevated temps = calcite growth



Sarah, Kae and others;

Something I left out form my last post but which should be obvious. If plants are using CO2 and HCO3, depending on species, there will be a depletion in both CO2 and Alk. So there will be Alk, CO2 and pH issue

 

[kae]

<a href=showthread.php?s=&postid=10040811#post10040811 target=_blank>Originally posted</a> by Boomer
If plants are using CO2 and HCO3, depending on species, there will be a depletion in both CO2 and Alk.

Do you mean Alk will decrease during photoperiod?

Thank you very much Boomer.

 

[Boomer]

Yes, they are decreasing the Alk just like corals do, both are using HCO3-, which is part of the Alk. True Carbonate Alk, CA is [HCO3-] +[ CO3--]. All of the coralline, Halimedia, etc, use up Alk and Ca++ just as corals. They produce and grow as a function of CaCO3 production either as Aragonite or Calcite. However, some alage do this more at night.

 

[3D-Reef]

Boomer, the problem I have is on the turtle grass blades.On the macros and the glass,I just swish some water and it comes off the macro's,a magnet cleaner and it's off the glass.But the turtle grass,I have to use the back of My thumbnail and scrape it off.
JMO I think at the surface level of the grass blade,photosynthisis is pushing Ph high enough to cause presipatation,eventhough Ph doesn't read high in the water column.
Does this make sense?

The average is;
Ph-8.0
Ca-380ppm
Mg-1250-1350ppm
Kh-8-9
No3-5ppm
Po4-.015ppm
If I try to raise these levels,(Ph,Ca) thats when I see a build up on the grass.

 

[Boomer]

Yes, that would be correct and is sometime seen in streams. I do not know what to tell to cure it. Kinda hard to control what the algae is doing at the surface water interface.

However, you are still more or less getting dust coatings on the glass and elsewhere. The only thing now that comes to mind is that one of the parameters, i.e., pH, Alk, or Ca++ is in error and actually is much higher. You should not get what you are getting unless there was some kinda' warm-cool water mixing in those areas and I do not buy that at all.

And what are all the additives you are adding ? When was the last large water change ? Who's kits ? Does this tank get any direct sunlight.

 

[3D-Reef]

The dust coating comes from adding a little more sand,to account for the loss of sand when harvesting macros.It really sticks to the grass but not to anything else.I don't add sand very often,just once in a while.

When I add kalk to the RO reservoir,any more than 1/2 tsp/8gals,I get the same build up on the grass.The Ph comes up to 8.3 and the Ca++ goes up to 400ppm.The evaperation rate is ~1.75 gals/day

All of the test kits are Salifert except for Ph,and it's made by Aquarium Pharmaceuticals.

The last large water change...40gals 2-3 weeks ago.

Additives...~1cup/week, Ca chloride-mixed at 2cups/gal of RO
Kent's turbo Strontium...5ml /week-mixed per instructions
Kent's super chelated Iron...10ml/week
Lugol's...2 drops/week
Kent's DKh buffer...3 tbsp/week
Kent's Tech-M Magnesium...as needed

No direct sunlight.

 

[Boomer]

3-D

On Monday, going to IMAC and need to get off this PC, it has been hrs on forums

 

[kae]

<a href=showthread.php?s=&postid=10043147#post10043147 target=_blank>Originally posted</a> by Boomer
Yes, they are decreasing the Alk just like corals do, both are using HCO3-, which is part of the Alk. True Carbonate Alk, CA is [HCO3-] +[ CO3--]. All of the coralline, Halimedia, etc, use up Alk and Ca++ just as corals. They produce and grow as a function of CaCO3 production either as Aragonite or Calcite. However, some alage do this more at night.

I think my question was not clear. What I would like to know is does Alk decrease when plants/algae (not calcareous algae) use HCO3- for their CO2 source to photosynthesize like in this equation?

HCO3- + H+ ----> CO2 + H2O

Thanks Boomer.

 

[Boomer]

Yes

 

[kae]

<a href=showthread.php?s=&postid=10049576#post10049576 target=_blank>Originally posted</a> by Boomer
Yes

Boomer, your answer made me confused. From what I've read and fromthis thread, I always believe that Alk does not change during photosynthesis if there is no calcification

Thanks for your help.

 

[3D-Reef]

<a href=showthread.php?s=&postid=10046099#post10046099 target=_blank>Originally posted</a> by Boomer
3-D

On Monday, going to IMAC and need to get off this PC, it has been hrs on forums

IMAC,sounds like alot of fun Have a good time!!

 

[graveyardworm]

The alk will decrease because the plant is removing the C from HCO3. So you no longer have HCO3, you are left with H and O3. Which are also likely to be used or converted further during the process.

 

[Boomer]

No David

The plant is removing the H /say and leaving more CO3 behind which increase the pH and lowers the Alk in the end. There is more to these reactions than this. Also, plants do not create ozone O3. This will help explain its complexity.

Photosynthesis and the Reef Aquarium Part I: Carbon Sources
http://reefkeeping.com/issues/2006-10/rhf/index.php

 

[graveyardworm]

Apparently I know very little when we start talking H+C-O3=:crazy1: but it was worth a shot.

I thought HCO3 was providing a source of carbon for marine plants. Isnt C Carbon? So wouldnt the plant be removing the C to satisfy its carbon needs?

 

[Boomer]

Yes, but you have to look at all the reactions taking place. Some plants can get their CO2 from HCO3- by converting it to CO2, which leaves " H and O " They then take the C out of the CO2 as their Carbon "C" soruce and give off O2 This loss of CO2 causes a net shift in the CO2 to be low, which raises the pH. CO3 can also be converted to CO2. Try reading the article it is all explained.

 

[graveyardworm]

I've browsed the article but havent fully read it yet.

 

[kae]

Boomer, would you please explain this statement.

Plants that do not calcify do not consume alkalinity. When they take up bicarbonate to attain CO2, they spit out OH-, leaving the alkalinity of the water unchanged:

HCO3- ---> OH- + CO2

That is what Randy has mentioned in this thread.

Thank you Boomer.

 

[Boomer]

Sorry Kae for not really answering you question earlier in a better way

There is nothing to explain. That is true. However, something I and Randy left out. Some plants are not calcifying or calcareous plants as we usually speak of them but do contain small calcium carbonate structures in their cell walls in small amounts, thus they consume some Alk. Some produce calcium sulfate. You may not think of soft corals at Alk users but many are as they have calcium carbonate spicules in their structure. Even things like sea urchins take up some Alk for their structures.

Since the plants are consuming HCO3-, a form of CO2 by conversion, there is a shift only in the pH, with no change in Alk. In this means it is the same as FW plants, which due not consume Alk but lower the CO2, which raises the pH.

HCO3- ---> OH- + CO2


This and similar equations are what pH is inherent to due to the shift I mentioned here;

As CO2 leaves the system it causes a shift in the ratio of CO2:HCO3-:CO3. At any pH there is an exact ratio of these. Anyone that has the same pH has the same exact ratio but the concentration may be higher. Since the ratio is the same there is no change in Alk. However, if the amount or concentration of the components of these ratios increases then there is a shift in Alk. This would take place in corals and plants that use HCO3- to produce calcium carbonate just like corals or if you dumped a buffer in your tank.


In NSW at 35 ppt that ratio is about @ 8.3 pH
<.4 % CO2, 93.6 % HCO3 - and 6 % CO3-.


Remmeber this is a ratio and not a concentration. So, if we lost HCO3- to plants, the Alk remains the same but the ratio above will shift to give a sligfhtly higher pH, so that new ratio may look like this .3 % CO2: 92.7 % HCO3- and 7 % CO3--

As I showed in a similar example on a post above, where two water samples have the same pH and differnt Alk we can do the same here where there is no shift in the Alk but there is in pH, a shift in Alk and not pH and a shift in both Alk and pH.


No shift in pH but consuming Alk

pH 8.3, Alk 2.25 meq / l = .4 ppm CO2
pH 8.3, Alk 2.0 meq/ l = .33 ppm CO2



No shift in Alk but different pH. Your -->where plants do not make calcium carbonate at all. The CO2 is lower and we have that increase in the ratio I posted above but still the same Alk.

pH 8.3, Alk 2.25 meq / l = .4 ppm CO2
pH 8.4, Alk 2.25 meq/ l = .28 ppm CO2



Shift in both Alk and pH

pH 8.3, Alk 2.25 meq / l = .4 ppm CO2
pH 8.4, Alk 2.0 meq/ l = .25 ppm CO2

 

[kae]

Thank you very much Boomer.

 

[Boomer]

You bet Kae