co2 in the aquarium

[catfishmike]

well with great apologys and a long mix -up here is a great article submitted by our very own 79camaro,who i once again want to apologize to profusely,thanks for typing this up.i will try to get this in the actual articles section as well.

While there are many different opinions about lighting, fertilization, and substrate, carbon dioxide is considered to be a necessity by most, if not all, aquascapers who are interested in creating dynamic, heavily planted environments. Certainly, success can be had without the addition of CO2, however the results will not be the dazzling aquariums which inspire so many aquarists to undertake a planted setup.

Carbon dioxide is the most critical plant nutrient (light not being a nutrient). Any stocked aquarium will provide plants with some CO2 (due to the respiration of aerobic organism, aka fish and other critters), and while this minute amount is often sufficient to maintain a few healthy plants, it can in no way fulfill the needs of a densely planted aquarium. When CO2 is not present in sufficient quantity plants grow very slowly and will tend to stay smaller. Furthermore, biogenic decalcification can occur; this is, essentially, a last ditch effort by the plants to obtain CO2 by breaking down the salts in the aquarium water. As this process occurs, the pH level can raise a couple points in a fairly short period of time. This alone is stressful enough for the fish, but the problem worsens when the lights are turned off. When photosynthesis stops at night, the plants will stop breaking down these salts and the pH will drop rapidly. This fluctuation is very harmful for the fish, but there is a simple remedy: provide the plants with a source of dissolved CO2.

So, now that the ill effects of carbon dioxide deficiency have been presented, the question becomes: how does one provide dissolved CO2? When the volume of water is large it is very difficult to supply and regulate the amount of CO2 necessary without a pressurized system and a regulator. A good analogy is a scuba divers tank. The bottle valve is always on and the regulator adjusts how much CO2 is injected into the water. This type of setup can be fairly costly, however it is certainly the most reliable means of controlling (and adjusting with ease) the amount of CO2 in the water. For small tanks, particularly those of 55 gallons and smaller, Do-It-Yourself (DIY) CO2 injection is often the cheapest solution. DIY CO2 is quite cheap. Aftermarket products are available to the person wary of actually doing the DIY themselves, however there is virtually no difference between these products and a simple DIY CO2 reactor and diffuser. The drawback to a DIY setup is the relative difficulty of adjusting the amount of CO2 injected into the aquarium. However, most people with small aquariums find that a DIY system works well, and the lack of regulation does not generally cause a problem with over-dosing. A simple DIY reactor can be built for around $10, considerably less than a pressurized system.

Building a DIY CO2 reactor is a great first project. It is relatively straightforward; all one needs is a 2L bottle, aquarium silicone, airline tubing (many people use silicone tubing because it derades less quickly), a check valve, and something to diffuse the bubbles (cotton balls and air stones both work, as will most anything with a fine mesh; some people use a bell type diffuser). First, measure the diameter of the airline tubing (it is usually 1/4", but there are other sizes). Next, using a power drill or Dremel tool drill a hole into the plastic cap of the 2L bottle. Frequently, the soft plastic seal on the inside of the cap must be removed at this point. The hole should be just slightly smaller than the diameter of the tube to help establish a tight seal. Insert the tubing from the top of the cap into the hole until it extends at least one inch through the underside. At this point, seal around the tubing on both sides with silicone aquarium sealant. It is important to do a good job filling all the crevices and gaps or else the CO2 will leak. Read the directions on the tube to see how long it needs to fully set; a day is a good estimate, however waiting an extra night will not hurt. If the sealant is not fully cured it simply will not hold, and that can be very frustrating. At some point in the tubing many people place a check valve. This is a good precautionary measure to prevent water from siphoning back into the bottle, especially if the reactor will be below the water level; a check valve is, however, by no means a necessary component of the DIY CO2 reactor. Two or more bottles can be connected together through the use of a T connector; brass is best because it will not dissolve as quickly as hard plastic; in theory, as many bottles as are necessary can be connected together. The placement of the tube outlet is really a matter of personal choice. Many people like to put it in the filter intake because this allows the CO2 more time to mix into the water; really, anywhere in the tank will work, though lower is generally better because the bubbles will have more time to dissolve.

So, now there is a beautiful DIY CO2 reactor sitting under the tank, but it is empty. There is one general formula for creating the CO2, but there are many different opinions on the proper measurements for the ingredients. One which has been successful for many people is a combination of 3 cups of white granulated sugar, 1 teaspoon of baking soda, and 1 teaspoon of yeast. The yeast consumes the sugar which uses the oxygen in the bottle and releases CO2 as a by product of this process. Combine these three ingredients in the bottle and fill it with lukewarm water to the area where the bottle begins to slope inward. Though it is not necessary, it is not a bad idea to shake the bottle up and try to dissolve as much of the sugar as possible. All that is left is to screw the bottle into the cap and watch the bubbles begin. Usually this process takes 10-30 minutes with full strength being reached within a few hours, however do not fear if it takes a little longer. Certainly, however, if no bubbles appear within 24 hours there is a problem and any seals should be checked. Most often the escaping CO2 can be heard hissing around the area where it is leaking.

A noticeable improvement in the growth rate of the plants should be visible within a few days, however certain things can prevent the CO2 from having its full effect. The most frequent problem is surface agitation; surface movement facilitates the release of dissolved CO2 into the air. This is particularly problematic with hang on the back filters when the water level is not raised to the edge of the filter outlet. Ideally, a canister filter should be used, however many times this is not an option, nor is it truly necessary; a daily check of the water level and topping off when required should be sufficient to prevent major problems.

Maintaining the appropriate amount of dissolved CO2 is an important part of a planted aquarium. Most planted aquariums require around 1 gram of dissolved CO2 for every 25 gallons of water. By comparing the pH value of the water and the carbonate hardness (KH) as determined through test kits it is easy to derive the milligrams per quart of CO2 through the use of a simple flow chart which is available from many sources, one of which is here: http://www.aquabotanic.com/charts.htm

Carbon dioxide is still just one part of the equation; the amount of CO2 necessary varies with the number of plants, fish, and amount of lighting. Experimentation is an important part of achieving the type of planted tank which can win praise and admiration, as well as provide satisfaction to those who view it. While it may seem complicated, it really is quite accessible with a fair amount of research, forethought, and patience.

[depthC]

Wow, great article. This seems to be a very thought out and thorough article and was very educational. So again props on the article 1979camaro.

PS - you may want to fix the link.

- depthC

[itchy armpits]

good job 79camero. im thinking of setting up a co2 system and found this article extremely helpful.

->just thought of a question. do i just rinse out the bottle and do it over again in a month or whenever the bubbling stops?

[depthC]

I may have some slight insight to your question itchy.

Ive heard that the gunk or i think the cultured yeast in the bottom of the bottle when you dump it out is beneficial. But I usually just rinse that out. Im not positive if its beneficial or not, so anybody else that can clarify this?

- depthC

[bigfoot150]

What is the purpose of the baking soda?

And don't u have to worry about PH fluctuation in hardwater with high PH?

[dial]

ok i have a question. say you pre disolve co2 into water (i have a fizzy drink maker so i can inject co2 into a 1 ltr bottle of water through it) if i was to turn the bottle neck down and submerge it into the tankl and leave it there (this is instead of just pouring it in) would the co2 mix into the tank water ???

does this make sense.

cheers aron.

[Avalon]

Yes, it will. There are fancy designs for this method of CO2 diffusion from ADA. Why don't you just inject the CO2 directly into the tank water? You can use your filter as a diffuser by injecting CO2 into your filter--out comes water with dissolved CO2. Of course, the CO2 will need to be regulated so that you don't inject too much.

[1979camaro]

lol...thanks guy...i just realized this was posted...lol

[1979camaro]

as for the link, i would love to fix it but cfm will have to do that

avalon's method of injecting into the filter will work as well, but i like to be able to see how much is coming out...

[catfishmike]

i fixed the link,sorry about that i didn't even notice it.