CO2 question

[graveyardworm]

Sarah and others, when dosing CO2 how do you know when there isnt enough, or too much?

I've been kinda discussing CO2 dosing with Anthony C. and whether or not he feels it may be somehow be detrimental to corals. So far his opinion is that it most likely isnt becoming limited, and that dosing it may do more harm than good.

I think I'm going to atleast start with a PH monitor, and determin what my daily fluctuations are. Is there a way to figure based on PH fluctuations whether CO2 is becoming limited or not?

 

[3D-Reef]

IMO,I think it's going to be like dosing Fe.Not so much as too have a dramatic effect,more that it's just available.
When I started Co2,I used a little to much yeast and the PH went down to 7.8.My Sarcophyton(toad stool) was the first to react by closing up.After a couple of days it came back out and didn't seem to mind.All the books I've read say the lowest PH to have is 8.0,I tend to agree.

The problem is Co2 is the first to be used by the plants,and is the last part of Alk requirement to be "filled" chemically.

Co2 when dissolved (carbonic acid H2Co3 ) first reacts with carbonates(HCo3-)to form bicarbonates(Co3=).Then the excess equalizes or cancels out with "free"hydrogen(H+) ions leaving more Hydroxyl (-OH) ions in the water,lowering the PH.

To figure out how much to dose,I would check the PH when the lights have been off for a while,like right before the lights come on,to see what the lowest point is.Then make sure carbonate reading is high enough to have at least an 8.0 PH. Then dose Co2 just enough to keep it at that PH when the lights are on.

 

[Samala]

I totally respect Anthony's advice and approach, always have. Just want to say: if CO2 (or carbon in general) isnt becoming limited then how do I explain continually high pH and low alkalinity levels in my un-supplemented seagrass tanks? Where is all the CO2 (which should help to depress pH as carbonic acid) and carbonate going?

Something in my tank is consuming vast amounts of carbon, and so far that organism prefers its carbon in CO2 form over carbonate form. Plants in alkalinity supplemented tanks grow just fine, but nowhere near the rates of those in CO2 supplemented tanks.

I never attempt to enrich my tanks for CO2. I dont try to depress the natural pH and drive it down to (what would be) acidic levels for an ocean environment. I use CO2 to keep the pH in normal levels (8.0 - 8.3 or so) and to keep the alkalinity erosion from beginning.

Ideally you'd use a tank/solenoid/valve setup such as used on freshwater tanks. That way you are always regulating pH within a given safe zone and dont run the risk of having too low of a pH (as Clay's Sarcophyton would testify too) or too high. My little amateur yeast-coke-bottle method is fine for smaller tanks, on larger tanks it doesnt produce enough CO2 to keep up with the demand. For really small tanks I wouldnt use it for fear of depressing the pH too much.

Anywho.. its all in how we monkey with the dosing I suppose. That will do a lot to play into how safe CO2 dosing might be into a lagoon like setup.

Ah, one more thing to mention. The pH from natural brackish water lagoon areas here, that support plenty of seagrass, macro and fish (but not much in the way of coral) falls in between 7.6 - 8.0 typically. So if you're running a seagrass only tank.. you might be able to push it that low without too much detrimental effect. Then again, you'd need to make sure you had estuarine fishes who would be okay with that approach.

>Sarah

 

[graveyardworm]

Thanks Sarah and Clay, I started searching outside the forums for alittle more info, but so far havent had much time. I did find one article from Zimmerman et al whom I'm sure all the plant people are familiar with. Here's one article regarding CO2 enrichment and eelgrass. Its just the abstract, and I havent gotten too far into the article itself, but it does seem to contain some really good info.

http://www.plantphysiol.org/cgi/content/abstract/115/2/599

 

[The Cardinal]

Hey guys I have been interested in seeing if C02 can have a benificial effect on the growthrate of marine flora for some time.

I culture two species of phytoplancton and was wondering if you have any view on using C02 with pytoplancton? I have seen some discussions here about C02 and macroalgae but never with phytoplancton.

Good discussion!

/Peter

 

[graveyardworm]

Have you checked over in the fish breeding forum, alot of phyto growers there, and I'm sure I've seen co2 mentioned there.

 

[Samala]

Mmhmm, absolutely. One of the major phytoplankton/plankton culturing manuals touches on CO2 enrichment for the growing media. I'll try to find the name of that guide.

>Sarah

 

[jrhupp]

David,

Thanks for the article link. That list of anatomical traits they give in the intro is identical to what you see in many fresh water macrophytes and is often prelude to something about a C4 based carbon concentrating mechanism. It blows my mind that one hasn't popped up amoung seagrass. Or has it and no one has identified it yet?

Sarah,

Are you familiar with the seagrass physiology litrature? Anybody looking at what these things are doing over a diel time course? Has photosynthetic capacity been looked at in a lot of species? Zimmerman et al makes refrence to the short term response they observed occurring in "many seagrasses", but only refrences Zostera and Thalassia specificly. Just curious. If you don't know, don't go out of your way to find an answer.

And not to get too sided tracked from the original topic, my take on CO2 enrichment is this: CO2 is by all means limited in marine systems. When it comes to our tanks, that is another question. In many homes where modern constructions methods result in very well sealed buildings reliant on recirculating HVAC systems CO2 concentrations can be many times that of outside (~360ppm vs 2000 to over 3000ppm inside). The effect on CO2 concentration in the aquarium will be much smaller than the 10 fold diffrence in air, but may provide enough additional CO2 to the system to make supplementation unneeded or dangerous. Alternativley, many sps dominated systems use calcium reactors to supplement calcium and other micro nutrients. Even the most effecient of these devices still delivers a fair amount of CO2 to the tank. These systems function just fine at lower pHs than what is thought typical for reef systems. With that said, I think the calcium reactor maybe a better aproach to dosing CO2 in marine aquariums as oppsed to adding CO2 directly to the water column, particularly in systems where coral are also target species. But, I have yet to try this (calcium reactor still in the works).


Jay

 

[graveyardworm]

Interesting you point out that a Ca reactor may be a better approach to dosing CO2. Eventually I plan to get one, and it become part of my reasoning for the investment in the CO2 equipment now. Any idea how much CO2 may actually be escaping into the display water? I dont fully understand Ca reactors yet other than the lowered PH causes the media to dissolve. Would i be a simple enough task to just up the amount CO2 going into the reactor to achieve dosing in the water column without adversely affecting the operation of the CA reactor?

 

[jrhupp]

David,

The product of dissolving CO2 in water is H2CO3 (carbonic acid). Which in the calcium reactor is mixed with CaCO3 to produce Ca++ and 2HCO3-. I can't see where an "excess" of CO2 would hinder the preformance if anything it would drive more calcium into the water. My feeling is that the residence time in the reactor is too short to use up all the CO2 in solution in the first place, hince the higher effluent pH of two stage designs.

Jay

 

[algaeguy]

Excellent discussion/points by all.

I think that Jay sort of hit it on the head with the last point that the residence time of the CO2 in the reactor is too short to utilize all of the CO2 to dissolve media. This might play to our advantage...

In my seagrass tank, I am purposely going with a calcium reactor with one stage, that is not super-efficient at using the CO2 being injected. I would hope that some of the CO2 does find its way into my system...How meaningful this amount is remains to be seen. My main goal in using a CA reactor was to provide some buffering and Ph support for the tank to smmoth out the day/night fluctuations I expect from a large amount of plants in the system.

I'm also curious if the effluent-delivered CO2 from a CA reactor is any greater (or more readily available) than the CO2 released into the system from animal respiration. I do notice a stable day/night pH, however.

Scott

 

[Limbo]

Can the CO2 gear for freshwater planted tank not be used?
http://www.marinedepot.com/md_viewItem.asp?idproduct=CO5111
If not, can someone explain why?

 

[graveyardworm]

I have no idea how the equipment pictured works, but I would say as long as the CO2 being mixed with the water can be measured ( bubble counter ) and the materials which come in contant with the water are salwater safe, then I dont see a reason why it couldnt be used.

 

[3D-Reef]

There is one thing I might mention about Ca reactors that hasn't come up yet.That is,a Ca reactor will keep Ca at or near saturation point.Then with Alk being at or near saturation point as well.Won't this cause any orthophosphate in the water to precipitate out to the sand bed?Making it unavailable to the roots or leaves?

 

[Limbo]

DIY CO2 System

 

[jrhupp]

3D-Reef,

That is an interesting point and something I had not considered. This maybe more important in systems without calcifing organisms (ie planted tanks), than those with (ie systems where the planted tank is only one component). And even in planted systems calcareous macros may place enough demand on calcium to prevent the precipitation of orthophosphate. Alternativley most higher plants secret substances into thier rhizoshpere that are used to make soil bound nutrients avaliable (citirc acid to make soil bound phosphate bioavaliable for example). It would not surprise me if some macros and seagrasses used similar means to extract nutrients from marine sediment. But this is just speculation.

Jay

 

[graveyardworm]

A link I found

DIY yeast method

 

[Limbo]

<a href=showthread.php?s=&postid=8308918#post8308918 target=_blank>Originally posted</a> by graveyardworm
A link I found

DIY yeast method

I only have one question....... can you drink it after fermentation? :beer:

 

[piercho]

Reefers (like Calfo) have tank systems that often have high rates of gas exchange between their system and atmosphere, and that influences their perspective on this. Many of the planted tanks I've seen on this board would have lower gas exchange rates than a typical reef tank system. If you have a fairly simple tank setup, without a overflow/sump or a protein skimmer the size of a trash can, it might serve your needs to use CO2 to lower pH towards equilibrium (around 8.2) during the light cycle. On the other hand, high system pH can usually be remedied by improving aeration. Utilizing a overflow-sump arrangment can make a big impact on gas exchange rates for a system, and can be a cheaper and more useful modification than a CO2 system, IMO. Overflows designed to entrain air in the falling water stream (like a Durso) do as good a job of forcing gas exchange as an air lift circulating a similar amount of water, IME.

So, I agree with Calfo to the point that increased aeration should overcome CO2 limitation - if that's what he meant. As far as a "danger" of using CO2 to lower pH in a marine tank, that is true but with some caveats. A "calcium reactor" is nothing but a CO2 reactor with calcium carbonate media in it. So, there are butt-ton of CO2 reactors out there in use on reef tanks, and for the most part being used safely by people who understand basic tank chemistry, IMO. That example is a much more elaborate and self-regulating CO2 reactor than a powerhead being fed CO2, however.

I should emphasize that careless or casual use of CO2 could harm or kill some marine creatures, especially invertebrates use to stable pH parameters. Improved aeration, on the other hand, facilitates tank stability and should tend to moderate pH near 8.1-8.3, assuming there is not elevated CO2 levels in the room. So, if the planted tank problem you are seeking to remedy is high pH, I would always recommend it be addressed by improved aeration rather than screwing around with CO2. I know that's not going to be a popular opinion but...

 

[Samala]

I know that's not going to be a popular opinion but...

Why would it be unpopular? Anything as moderate and clearly thought out should be widely welcomed by anyone cruising these boards. There is something to be said for the KISS method afterall.

I think you bring up an excellent point that the setups I've been playing with are going to be lower in gas exchange rates than the common reef aquarium. Its just the nature of my comfort zone I suppose.

Its also going to be an artifact of the fact that I, originally, intended my seagrass lagoons to be somewhat lower energy than any reef would be - I wanted seahorses and pipefish as inhabitants initially.

Tom Barr has mentioned that protein skimmer's would be valuable mostly for their aeration on a marine planted, and you're hitting on the same overall concept. But.. overflows, surges, dump buckets, etc.. might likely be a better bet for improved exchange overall.

>Sarah