Which tank could get away with less light: non CO2 or a CO2 enriched tank?

[plantbrain]

And of course, why? Explain.

This question came up in discussion of the low light in the ADA hoods.
I posed it and many thought it was the non CO2 aquarium.

Regards,
Tom Barr

[Church]

Both. Because low-light tanks don't need CO2 enrichment, yet having CO2 enrichment does not negatively impact low-light tanks.

Did I win?

[macclellan]

Without testing it, I'd say the same as Church - the same. This is assuming all else equal (stocking, feeding, fert regime, maintenance, etc). CO2 wouldn't be the limiting factor in either case - light would be. At best, I'd think the co2 enriched tank would do better. At worst, it would be a waste of co2.

[Allen121]

My assumption would be that the non-CO2 infused tank would get along with less light as opposed to the CO2 infused tank, due to the fact that the light is what permits the plants to make use of the CO2 in the first place from what I've read, so CO2 infusion into a low light tank (within reason) would be a waste at best, and cause an imballance leading to algae blooms and possible cyanobacteria at worste. It would not adversely affect the plants directly, but the results it might have on the water chemistry certainly seems like it could. This is all assumptionhowever based on a lot of reading recently, as I've been toying with the idea of increasing my light output and creating a DIY CO2 system for my own tank, so pardon my "newb ignorance" if I'm way off base, LOL!

[original kuhli]

never mind...read the question wrong...

[dogdoc]

I'm gonna go out on a limb and say the CO2 tank.

My experience starting out was to go with a triple tube strip light on my 75. No CO2, ferts etc. The plants lived, but I wouldn't really say grew or thrived. I had to make a choice of what to upgrade first and chose a pressurized CO2 system. Without changing any other variables, the plant growth really increased, and all the plants looked better.

[original kuhli]

Exact same experience here dogdoc, 160 watt over a 135 gallon tank, poor growth before CO2, great growth with CO2 and no ferts. You have to think that the CO2 affords the plants a better ability to compete with algae for nutrients.

After all...that's why this post is here isn't it!

[plantbrain]

Hint time:

http://www.tropica.com/go.asp?article=792

Read this and each of the parts.

Then decide.


Regards,
Tom Barr

[JDowns]

I won't answer because of an unfair advantage in having discussed this quite awhile ago.

But I will fix your link. As I believe this is the article you are referring to.

http://www.tropica.com/article.asp?t...aristic&id=835

or I could be wrong and its the four part series eluded to in the above article

http://192.38.244.204/article.asp?ty...aristic&id=142

[JDowns]

I think people that have had problems with HC or other termed "high light" plants should read that thoroughly.

[plantbrain]

Thanks for the link fix.

That's not my personal source, but describes the issue well enough for folks to get the answer. And it's one of those articles that's been around for sometime, but many many new folks have never bothered to read.

Regards,
Tom Barr

[original kuhli]

My summary:

CO2 is the principle limiting nutrient in aquatic systems. One can therefore assume that even in a lowlight tank CO2 and not light is the limiting nutrient for photosynthesis.

Even low light tanks need CO2, and a CO2 enriched tank will provide for greater photosynthesis than will a non-CO2 enriched tank.

(note the use of the word assume)

[Church]

Okay, so unless you worded your original question ambiguously, I still believe the answer is "both tanks can handle less light." I just finished reading that article, and I believe it confirms my stance.

Unless you were trying to say "which one of these tanks, a co2-enriched one and a non-enriched one, would be the most efficient at photosynthesis under low-light conditions."

But that's not how I read it. Nor, it seems, is that how macclellan read it.

What's my prize?

[bsmith]

What would happen if you injected co2 to say 30 ppm in a low light tank >1wpg? Would it have the same side effect as over dosing nutrients?

[plantbrain]

Originally Posted by original kuhli

My summary:

CO2 is the principle limiting nutrient in aquatic systems. One can therefore assume that even in a lowlight tank CO2 and not light is the limiting nutrient for photosynthesis.

Even low light tanks need CO2, and a CO2 enriched tank will provide for greater photosynthesis than will a non-CO2 enriched tank.

(note the use of the word assume)

Your rational is correct.
Think about the law of the minimum that Liebig discusses.
Now think about which are the most limiting, light or CO2?

If you read the article and read it carefully, a plant requires less resources to be allocated to "catching CO2" in an enriched high CO2 tank vs the non CO2 tank. This means the plant has more resources to "catch light".

Both Chl a and Rubsico both are very nitrogen rich molecules, so if you need less for Rubsico, the CO2 catching enzyme, then you have more resources to allocate for Chl a.

Thus the CO2 enriched system will be able to grow at a lower light intensity and have a lower minimum thereshold of light, the light compensation point.

Generally, the advice on most forums is to not use CO2 under lower light situations, however, this is counter to what is observed and theorized if you think about things in the above terms.

Low light reduces the rates of growth, a great deal and can slow them way down(by a factor 10X or so) even if you are using CO2.

Light is the critical part here.
Many folks suggest adding more light for better growth, while true if the CO2 supply is still the same and increased appropriately as well, often folks don't do that.

The general point is that folks may consider adding CO2 before considering the addition of more light. I think folks will have more success overall and much less algae.

But so many folks think they must have higher light or they need it for so and so species of plant, or for better colors etc.

Leggy plants take some time to adapt to the current conditions and if you change them, they will reach for light, but after a ,month or so, they are fine and have adapted to lower light.

Enzyme and biochemical reorganization does not happen instantenously.
It can takes a few days, weeks etc. When folks see leggy growth, they think it means the plants will always do this under low light.

The rates of growth are also important, it's easier for a plant to assimilate nutrients from fish waste, various other sources such as the sediments and the water column, thus you have better growth appearance, but slower growth, a general consensus many desire.

The folks that often buy CO2 generally bought too much light, and it's often rare folks buy CO2 first, and keep their low light.

So you get HLD........

And folks are generally an impatient lot.

There is a case, at leats in theory where one might have equal limitation power on both light and CO2 at the same time, but this is a theoretical knife's edge, very hard in practical terms to have.

One way or the other, the see saw tips.
So in practical terms, not going to happen. I does happen in some cases where N and P bob back and forth in highly limited ocean systems. Co limitations can occur, but they generally go back and forth.

Adding more light will also reduce the demand for Chl a, as less is required, but this works much less so, algae, unlike plants, are not CO2 limited.....they are in general, light limited.

So you can have non CO2 tanks with higher light and easier to grow species that are aggressive and able to live pretty good under CO2 limited conditions.

Read the Tropica article a few times.

You will get it.

Regards,
Tom Barr