Oh man, where to start. Jose was nice enough to stop by and ask for some pics for a redo.
CO2 is tool, it can amplify growth by 10-20X if the light and nutrients are independent, in other words, non limiting for the plant/s in question.
So we add CO2 to grow plants better, and without competition by other more aggressive plants that hog and take up CO2 much better than other species.
Plants still grow without adding CO2 gas.....they just do so much slower.
Ole and Troels did a CO2 and light experience to illustrate this:
http://www.tropica.com/advising/technical-articles/biology-of-aquatic-plants/co2-and-light.aspx
Look at figure 3.
We have 3 different light intensities and 3 different CO2 levels.
In all cases, the plant still grew.
The difference was the
rates at which they grew.
Egeria densa is a very strong CO2 user, aggressive and can also use KH or the HCO3/bicarbonate whereas something like Ludwigia panatal cannoit is not as aggressive. L panatal will still grow in absence of other strong competitors or without high biomass, but when you add higher biomass/more species with different CO2 compensation and saturation points, then it becomes much harder.
This is why we have trouble growing many species in non CO2 tanks, but these same species grow just fine with good CO2.
Still, I can grow most species in a non CO2 tank, I just have to be careful about the % biomass and the species I chose if I want a wimpy CO2 demand plant, vs say an aggressive weed like Egeria.
There are many papers of how CO2 enrichment affects growth rates, typically about 10X as FAST, so 1000%. That's a lot. But as Ole andf Troels conclude, using less light reduces the rates of growth and makes CO2 management much easier and light usage much more efficenct.
So I can get more growth using less light, so I do not need to spend so much of light, and I also do not waste $$$ and energy on excess light. This cost far more than water and drives everything related to growth rates, it all starts with light, not with nutrients, and not with CO2.
I suggest folks learn how to master both CO2 and non CO2 methods, some do Excel etc, those are more similar to CO2 enrichment methods however.
We have different goals as aquarist, so no one method will be the best choice for all goals. We can look at figure 3 to see several choices to pick and chose for both light and CO2, nutrients are non limiting thus independent in the Tropica example.
Here is a non CO2 tank without a water change for 2 years:
Here is another with CO2 that makes more $$ off plants and shrimp than any other planted tank I've seen.
Different goals, but both are successful nice tanks and the fish are healthy.
I do not view CO2 enrichment as a requirement, but many seem to assume automatically it means we should add more light, this is incorrect. We want more growth, more efficient use of light and a wide selection of species to garden with, we are not looking to maximize yield and get as fast a rate of growth as possible.
Liebig's law also applies to cO2 and to light.
So we can provide CO2 and nutrients non limiting, and then reduce the light down to control the rates of growth which we desire.
Unlike nutrients or CO2, light is the most stable parameter we provide and it also has the highest cost for waste. CO2 and nutrients are cheap. So chosing light to mange the rates of growth that best suit you and your habits is a wise choice for many.
This makes CO2 dosing and nutrients far easier.
Enriched sediments also makes dosing water column ferts easier as well.
More wiggle room.
Algae are never CO2 limited in an aquarium.
Plants very often are.
BTW, there are plenty of examples in natural system where the CO2 is 20-40ppm, Bonita Matogrosso Brasil, hundred's of FW springs in Florida, Pupu springs in NZ, a dozens in China, San Marcos in TX etc etc.........
packed with fish etc.
You just need to know where to look.
Read the Tropica article carefully, then again a few times, make sure you understand what they are telling you. It should clarify many things.
Regards,
Tom Barr
