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#1
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CO2 in low light situations.
Is CO2 beneficial for plants in a low light(1-2 wpg) application or
should it only be used in 2 wpg+ applications? Thanks, Scott |
#3
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CO2 in low light situations.
On Fri, 22 Nov 2002 16:49:36 -0700, Chuck Gadd wrote:
At medium light: Low CO2 = 3.3% growth Med CO2 = 92.% growth High CO2 = 10.3% growth (a 212% increase over low CO2) Hopefully you all figured out that the Medium-light, medium CO2 growth was 9.2%, not 92%.... Chuck Gadd http://www.csd.net/~cgadd/aqua |
#4
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CO2 in low light situations.
In article ,
Chuck Gadd wrote: On Fri, 22 Nov 2002 20:55:39 GMT, wrote: Is CO2 beneficial for plants in a low light(1-2 wpg) application or should it only be used in 2 wpg+ applications? Thanks, As Tom Barr, and Claus Christensen over at Tropica have observed, even low-light tanks will benefit from CO2 injection. And it does make a lot of sense. Plants need Light, CO2, and nutrients. If the light level is very low, plants need to work harder to utilize that light. If the CO2 level is very low, plants need to work harder to utilize that CO2. If the plant is spending its energy to utilize CO2 and light, then that energy can't be used for growth. So, if you supply more of light or CO2, then the plant doesn't have to work quite as hard, and so it has a little more energy left for growth. At the AGA Conference, Claus showed a chart, showing differences in growth rates based on low or high light and CO2 levels. At low light and low CO2, the plants must expend high amounts of resources to assimilate CO2 and capture light. The plant (Riccia in this case) grew at a rate of 1.1% per day. With low CO2 and high light, the plant still needs to expend high amounts of resources to assimilate CO2, but less to capture light. This means there is extra resources in the plant for growth. The plant grew at 6.5% per day. With high CO2 and low light, the plant expends high amount of resources to capture light, but less to assimilate CO2. The plant grew at 4.1% per day. And when provided with high light and high CO2, the plant was able to utilize all of its resources for new growth, resulting in a growth rate of 14.8% per day. Another chart showed the effects of the various levels of light and CO2. Three levels of CO2 and three levels of light were used. Low, Medium, and high CO2 were defined as 0.7mg/l, 6.6 mg/l, and 35.2 mg/l Low, Medium and High light were defined as 1400 lux, 5400 lux, and 15200 lux. At low light: Low CO2 = 1.1% growth Med CO2 = 3.8% growth High CO2 = 4.1% growth (a 272% increase over low CO2) At medium light: Low CO2 = 3.3% growth Med CO2 = 92.% growth High CO2 = 10.3% growth (a 212% increase over low CO2) At high light: Low CO2 = 6.5% growth Med CO2 = 10.5% growth High CO2 = 14.8% growth (a 127% increase over low CO2) (Note, the percent increases were calculated by me, so if they are wrong, it's not Claus' fault!) This tells me that CO2 can have more impact on low-light tanks than on high light tanks. But, in high-light tanks, CO2 is manditory, because otherwise, with the massive amount of light, if the plants are CO2 limited, algae will thrive. Chuck Gadd http://www.csd.net/~cgadd/aqua Excellent info Chuck. Thanks! Scott |
#5
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CO2 in low light situations.
In article ,
Chuck Gadd wrote: On Fri, 22 Nov 2002 16:49:36 -0700, Chuck Gadd wrote: At medium light: Low CO2 = 3.3% growth Med CO2 = 92.% growth High CO2 = 10.3% growth (a 212% increase over low CO2) Hopefully you all figured out that the Medium-light, medium CO2 growth was 9.2%, not 92%.... Chuck Gadd http://www.csd.net/~cgadd/aqua Thanks for the correction. I was going to shoot for 92% growth. :^) Scott |
#6
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CO2 in low light situations.
On 23 Nov 2002 01:37:07 GMT, oSpam (LeighMo) wrote:
to 6.6 ppm. But few tanks have as low as 0.7ppm, at least if you have decent water movement. So "low CO2" really means "seriously CO2 deprived" on this chart, and doesn't really apply to most tanks. Am I understanding the data correctly? Yes, but a non-injected tank is somewhere between that 0.7ppm and 6.6ppm. A non-injected tank with good aeration will stay right around 3ppm. So it's half way between the "low" and "medium" steps. I definitely think that injecting CO2 into low-medium light tanks is a smart thing. Chuck Gadd http://www.csd.net/~cgadd/aqua |
#7
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CO2 in low light situations.
And it does make a lot of sense. Plants need Light, CO2, and
nutrients. If the light level is very low, plants need to work harder to utilize that light. If the CO2 level is very low, plants need to work harder to utilize that CO2. If the plant is spending its energy to utilize CO2 and light, then that energy can't be used for growth. So, if you supply more of light or CO2, then the plant doesn't have to work quite as hard, and so it has a little more energy left for growth. There are few other good ideas that spin off this concept. One is algae. Algae growth is reduced, herbivores don't need to work as hard(slower algal growth). The aquarist spends less time pruning and scrubbing algae. In a similar way, very low NO3 for example will reduce PO4 and NH4 uptake, basically stunting a plant through starvation. It won't necessarily kill the plant, but it's not doing much(and becomes a good place for algae to grow) it just stops growing until the nutrients are available again. Only severe nutrient deficiencies will result in death of the plant. The more pieces of the nutrient/CO2 equation that are put together, the more flexibilty one has with other factors and parameters. To gauge things like light, a tank is set at an optimum, then manipulate one paratmeter at a time to see how the system responds. Adding High CO2 and nutrients allows the light to be the limiting factor. Adding high nutrients and light allows the CO2 to be the limiting factor. Adding high CO2 and light allows the nutreints to be the limiting factor. Adding high light, CO2, PO4, K and NO3 allows the Traces to be the limiting factor. And so on.......... Most of the issue for folks is knowning what these optimum ranges are and being able to maintain them long enough to consider the parameter they are wanting to manipulate. This is/has been confounded with poor testing and test kits, no standards to test these kits against etc. Regards, Tom Barr |
#8
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CO2 in low light situations.
I would think that
eventually, you reach a point where plants are growing so slowly that more CO2 doesn't help plant growth, any more than overdosing fertilizer in a low-light tank does. Leigh Yes, you do get to that point, but still, it allows the plants to fully utilize all the light that's there. Think about light "limitation" Think about CO2 limitation. Think about Nutrient limitation. How do you test the effects of each? By adding _all_the_ other_ parts to slighty "excess" for the plant's optimum needs. Then manipulate your variable, in this case light. High CO2, high nutrients. For nutrients: high light, high CO2. For CO2, high light and high nutrients. Then you know who's doing what and what effect it has. Since algae love high light, can live on next to no nutrients(ruling out limiting them via nutrient limitation), adding CO2 and or lowering the light are viable options. CO2 affects different algae differently. Mostly negative though(All algae can use HCO3, but only a FEW PLANTS CAN). So limiting light slows their growth down, to the point in some cases were you don't need to clean the glass except once every 1-6 months. I use a shop light(2x40W) over a 55 gallon tank with a reflector. That's about 1.67 watt/gal. This does very well. Nutrients levels are the same for low or high light tanks, but the dosing required is less frequent for the low light tanks(weekly works fine in most cases) Regards, Tom Barr Regards, Tom Barr |
#9
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CO2 in low light situations.
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