What says I need CO2?

JoelB

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Jul 17, 2008
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Is it the case that the plants simply grow more slowly or is it not as simple as that. If I have more than a certain amount of light (and the right nutrients) will a low C02 (as in natural levels without equipment) actually cause problems?
 
If you have above a certain amount of light, the lack of additional co2 will result in algae issues.

Typically that amount of light is 2 wpg, but it's not as simple as that and if you are in the 1.8 wpg to 2.5 wpg you may or may not need co2 depending on tank size. Tanks with 2 wpg or more without co2 are the exception, not the rule. Generally, if you are planning to put 2wpg or more on a tank, you need to plan on co2.

However, it's a package deal. If you have light that requires co2, you will also require the regular addition of fertilizers.
 
I agree with jm, though will add the point where CO2 is needed may also depend on the efficiency of lights (t12s vs t5s), reflectors and the height the lights are mounted above the aquarium.

...will a low C02 (as in natural levels without equipment)...

I think this is a common error in reasoning. An aquarium bears little resemblance to anything "natural". Nutrient levels in natural bodies of water can be extremely low but due to the volumes of water involved will be essentially limitless for plants. Plants in the wild can supplement CO2 as a carbon source with the soil they are rooted in. I would say the majority of aquarists do not use soil in their tank.
 
So if I use soil I may get away with a little more light for the same C02 reading?
 
Within limits, I believe so but generally light levels are kept lower than "hi-tech", this method is still predicated on slow growth. Personally, I've never done a "natural planted tank" which is how they're usually referenced. Aquaticplantcentral has a forum dedicated to them. Also note this is a specific regime that has its own advantages and disadvantages. Alot of people get themselves into trouble when they mix and match techniques from different methods. The biggest advantage to this system is less tinkering, pruning than high light tanks. Due to the soil substrate, aquascapes tend to be dominated by slower growers since uprooting plants from a soil substrate can get messy. If you like to tinker with your tank, than obviously these are disadvantages.
 
So if I use soil I may get away with a little more light for the same C02 reading?

This gets into what is called a "Naturally Planted Tank", where soil is used as the substrate and they are still generally low light tanks. Most NPT's do not even use added lighting, they are simply placed in a window for sunlight.

NPTs are require a bit more than just adding soil, so if you wanted to go down that road, you'd need to read up on it a lot. Without the proper planning and understanding of NPTs, adding soil to an aquarium will only result in algae and dead fish.
 
If you would like to experiment with carbon to see what kind of results you can get, try dosing with flourish excel. You won't see the same results as CO2, but you will get a feel for what's in store. In the long run, maintaining a tank with excel will get pricey. Whereas CO2 is more of an up-front cost but is the cheapest over the course of time.
 
You can always try the level of lighting you want without CO2, observe the results, THEN decide if you would like to try flourish excel or a CO2 system.

You might also like to look up "Ecology of the Planted Aquarium." Here's a link to some reviews. http://www.aquahobby.com/books/e_walstad1.php

Walstad explains nutrients, microbes, soil, lighting, and tons more.
 
In all of my planted tanks I use potting soil under the substrate for nutrients. I have the oldest of the tanks planted with Miracle Grow Organic at a layer of 2" and apx 2" of playground sand covering that. I have not had any issues yet with hair algea or the dreaded BB algea and my photo period can be as long as 14hrs a day. The main tank is inbetween 2 large windows and I turn the light strip on when I get up and off when I go to bed. This works well for me simply because I have healthy plants and do not have to trim them every day. I have not dosed one ounce of ferts, or added one bubble of CO2. I do keep all low light plants and have a pair of 4' 5000k 40w lights. This tank is 72 gallons so we're talking about just over 1 wpg plus natural light.

plant list for that tank: Anubias Lanceolata (at least 1" of rhizome growth in 8 months), Bolbitus fern aka. African water fern (countless new fiddleheads and runner growth of more than 3") crypt lutea (unbeleavable growth, started with 1 pot split into 5 plants, now I just split one of those into 5 more plust several runners resulting in new plants), crypt california sunset (moderate growth), undulatas (sp?) have now grown to the waters surface and across the top several inches, 1 amazon sword grandfolias has emerged from the surface and now stands a whopping 24" tall from sand to open air. 1 ruby melon sword that has more than doubled in size with apx. 10 new leaves, a bit of java moss here and there, and Guppie grass that I have to cut back about once a month.

I have a trio of Long Finned - Blue Eyed - Albino bristlenose plecos that keep everything cleaned up really well for me, and I think the Guppie grass sucks up alot of extras out-competing the algae for goodies. Low tech success in my humble opinion. I am enjoying the tank greatly for a small investment and a manageable maintence schedual.

A quick word on Miracle Grow Organic potting soil though. Lots of biological material. Wood shavings and shreds galore. Some tannin staining of the water and believe me they find their way to the top without much trouble. It has made what I thought would be a nice white sand bottom look like the bottom of a river bed. Witch, actually, is not such a bad thing. It looks very natural but has a tendency to clog the filter pads in the penguin filter pretty quick. I rinse them in tank water about every other week when I change the water. I have gone as long as 1 month between changes and have had no fish loss, but I try to keep an every other week w/c schedual. In the tanks I have set up since I have gone with Fertilome Ultimate potting soil. Unfortunatly I have not had them set up long enough to compare the growth between the two.
 
So if I use soil I may get away with a little more light for the same C02 reading?

Wet soil is naturally host to much decay, as it is full of organics and bacteria. Decay produces CO2 in virtually all environments. If the cap on the soil is permeable enough, a lot of CO2 will escape by diffusion into the water column. Plants can absorb CO2 from soils and from the water, and CO2 is so soluble in H2O that it will exist in greater concentration, out of equilibrium with the air so long as your filtration doesn't blow it off with excessive aeration. If the cap on the soil seals the CO2 in, it will become saturated and then begin to form bubbles, which will break through and rise to the surface without adding much to the water. Roots, however, can still access the saturated CO2 if they penetrate the cap down to the soil.

Get a CO2 test kit and compare levels with those recommended by ADA with their pressurized CO2 infusion kits. If its even vaguely comparable, by all means try more light than NPTs use.

I have a freshwater DSB, heavily planted, and set up so mulm sifts down into the sand and decays, which releases CO2. My plants grow like nuts with 2wpg 12000K CF light. I should get a CO2 test kit.

I'm positive soil gives a CO2 boost, but the question is how much? Is it enough for fast growing plants to take advantage of strong light? This requires investigation!
 
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