CO2-Why & How To

(by AJB March 12,2003)

Introduction

More often now your starting to see pictures of amazing planted tanks. Many people wonder how to do this and wonder about the methods and such a person uses to start and maintain a planted tank, and it is indeed a rather complex subject.

Basically, there are three secrets to having a successful planted tank: light, CO2 (carbon dioxide gas), and nutrients. This article is about CO2, a very important part of a planted tank. Carbon dioxide is a substance that plants use to go about photosynthesis and make food, along with sunlight, water, and minerals. It is a very important thing to have, and there are three ways to get it.

Injection Methods

The first, and the easiest, is to do nothing but make surface agitation as low as possible. This is not very effective at all, and the most CO2 you’ll ever get doing this is maybe 4 ppm (parts per million). This isn’t nearly enough to make your plants what they could be, and if your any kind of a plant enthusiast you’ll take it upon yourself to at least try and inject CO2.

The second and the next best way to inject CO2 is by using yeast, sugar and water to ferment and produce CO2 (among other things). This is a very simple process and easy to pull off. The basics of it are to get the ingredients into a 2 liter bottle and inject it into the tank. This method is much better then the first, and in small tanks will be able to allow you to grow plants worthy of staring at for hours.

The third and final is by using a CO2 tank and regulator. In the CO2 tank, it will remain as a liquid at about 900-1000 PSI (pounds per square inch) of pressure. You use other components to reduce this pressure to something along the lines of 10-120 (or more) bubbles per minute. This is by far the most effective form of injecting CO2, and if your serious about your plants to the point of not caring about your fish, this is the way to go.

Words To Know

Along your quest of setting up some form of CO2 injection, you’ll run across some terms you may or may not understand. This is a list of them and their definitions.

Bubble Counter-a simple device used to count the rate at which CO2 is being injected into the tank.

Ceramic Diffuser-A very fine pore type of “co2 stone” that takes the CO2 input and turns it into very small bubbles, thus allowing the carbon dioxide to be absorbed.

Check Valve-A one-way valve that allows something to go one way, but not the other. The best kind for CO2 use are the brass ones, or ones specially designed for CO2. Regular air check valves tend to build up crud and rot away the flap that allows it to work, although I have used air ones before with luck.

CO2-The substance Carbon Dioxide, which animals exhale and plants inhale.

Diffusion Bell-A bell-shaped chamber which traps CO2 as it bubbles into it. The CO2 then diffuses into the water.

Diffusion-Not to be confused with the term diffuser, this is the word used to describe CO2 (or anything else) atoms mixing with H2O (or anything else) atoms, and thus allowing water plants to absorb CO2.

DIY CO2-a method of injection carbon dioxide into a tank by using yeast, water, and sugar.

Glass Diffuser-See Ceramic Diffuser

High Pressure System-A method of injecting pressurized CO2. Not as accurate as the low pressure method. The setup goes like this:
Tank > Regulator > Check Valve > Reactor/Diffuser

Low Pressure System-A method of injecting pressurized CO2. More accurate then the high pressure method. The setup goes like this:
Tank > Regulator> Needle Valve > Check Valve > Reactor/DIffuser

Needle Valve-a valve used to control CO2 into the tank. It is very precise. Some can go down to 1 bubble per minute, up to “honey, the fish are dead”.

Reactor-A chamber where the CO2 enters and rises, but is met by a stream of water going down. The water forces the CO2 into smaller bubbles until it dissolves into the water. This is the best means of getting co2 into the water.

Regulator-A device used right after a CO2 tank on a pressurized system. It takes the extreme pressure in the tank of about 1000 PSI down to about 2-10 PSI, where it is manageable.

Solenoid Valve-a valve used with pressurized CO2 systems. There is a PH sensor that detects the PH of the tank water and tells the valve to adjust the flow accordingly.

How to: the DIY method

The first thing that you must do is get the parts.
 

• 2 liter pop bottle(s) and cap(s)
   
• yeast
   
• sugar
   
• warm water
   
• drill and bits
   
• aquarium or silicon air tubing
   
• a check valve
   
• a way of diffusing the CO2 into the water

Assembly

1. Get a drill bit slightly smaller the 3/16” (air tube). Drill a hole into the cap of the bottle, and insert the air tube. The way I do this is by cutting the tube at an angle, then putting the tip of it through and using needle nosed pliers to pull it through. You’ll hear about people using silicon sealant to help seal it up. You can if you wish, but note that if you make the hole a bit smaller then the tube you shouldn’t need to do this.

2. Mix up the yeast solution. There are many different recipes for this, some using ingredients such as jello and such to make it last longer. I have never tired the jello method, but I have heard it lasts up to a month. Here is the recipe I usually use:

Put 1/4 to 1/2 teaspoon of yeast into the bottle. Generic bakers yeast will work, but some people use wine or beer maker’s yeast on the theory that it won’t die as quickly due to alcohol poisoning.

Add in some water, filling the bottle maybe half full. Use luke warm water, as cold water makes it harder to dissolve the yeast and the sugar and hot water kills the yeast. Shake the bottle up to dissolve the yeast.

Add 1 to 2 cups of sugar and again shake well. If your water level is lower then the part before the curve of the bottle, then you can add more. However, if it is at or above, you don’t want to add any more and may even want to take some out. I have on several occasions got yeast solution into my aquariums and it is a pain.

3. Run the CO2 line into the aquarium, through a check valve, and terminating in the aquarium. Pick a diffusion method, and have the CO2 bubbles go into your reactor of diffuser.

Notes: * Experiment your yeast recipe until you get satisfactory results. More yeast will result in stronger CO2 production, but deplete the sugar faster and create alcohol faster. More sugar will result in longer CO2 production, but eventually it gets to the point where the yeast dies from the alcohol before it uses all the sugar.

**Some people use rigid glass bottles instead of pop bottles. The reason for this is that if you have the co2 line close to the input of a powerhead or a canister filter, it may collapse the bottle and start to suck the yeast and sugar solution in. You may do this if you plan on using a powerhead or a canister filter for dissolving the yeast.

Injection Methods

This method uses a powerhead to inject co2 into the tank. It is hard on the impeller and sometimes makes a fair amount of noise, in addition to not being as efficient as other means. I don't generally use it, unless it is a very small tank.
 

This method uses something to catch the CO2 and let it diffuse naturally. I use it when I don't want to buy a new powerhead, or in smaller tanks. I used it for a while in my big tank and the highest I could ever get the CO2 was 10ppm.

This is a very efficient method that I use in my 46 gallon tank. I recommend to everybody, since it is easy to make and very efficient. One thing to not do is make the tube to short, or some bubbles may escape. I have this problem now, to a small extent.



© 2003. Do not use without permission. If you have any suggestions or ideas on the layout of this article or things to add or edit, let me know. Full credit will be given to you.
 

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