Build Your Own Yeast CO2 Generator

The easiest way to provide your planted aquarium with CO2 gas (a vital fertilizer) is to make your own yeast powered CO2 generator. This can be done very easily and inexpensively (all you need to buy is tubing and the supplies for the yeast recipe). Below are the tools and supplies required:


Any juice container will work, or any container with a tight fitting lid for that matter. However, some containers work better than others. I've always had good results with juice containers whereas some of the othe containers I've tried (like the big iced tea jugs) don't make an airtight seal when closed. You can use any size, however 48-64 ounce containers are a good size. They fit the 2 cups sugar called for in most recipes and don't take up a huge amount of space. The bigger the generator, the more water there is which dilutes the alcohol byproduct that eventually kills the yeast, so larger containers will last longer as long as you add the same amount of ingredients. The tubing can be any kind of airline tubing, however standard airline tubing will eventually go hard and crack from exposure to CO2. Using silicone or CO2 resistant tubing is best. A drill is nice, but if you don't have one, the same result can be acheived with a nail or screw.

Step 1

Drill a hole in the lid smaller than the diameter of the tubing, but large enough so you think you'll be able to squeeze it through. I use a smaller drill bit and then widen the hole with a pair of aquarium tweezers. Remember you can only make the hole larger, so don't get overzealous.

Step 2

Cut the end of the tubing on a diagonal and push it through the hole in the lid as shown, using tweezers or pliers to grab it on the other side and pull it through. If it doesn't seem to fit, make your hole bigger. If you don't need pliers or tweezers, the hole is too big and CO2 will leak out. If this happens, you need a new container (or at least a new lid). Pull it through only a half an inch or less.

Step 3

This is the finished cap and tubing. The seal should be tight enough to prevent leakage. There is no need for glue or silicone if it is done right. Just screw the lid on and you're ready to mix up your yeast solution!

The Final Product: A DIY Yeast Generator

There are a few important things to remember about DIY yeast generators.

• First, they are under pressure. Although it is highly unlikely they will burst, it does happen if the tubing gets clogged. Make sure the gas has a clear path to your tank. Some people add a check-valve between the tank and the generator to prevent yeast bubbles and goo from going up the tubing. Personally I've never had this happen and adding a check valve only makes another possible leakage point. As long as you don't overfill or shake up your mixture, it shouldn't get into the tubing.
  
• Also remember that if you squeeze the bottle (even gently), once you release it, it will suck up aquarium water. This can form a siphon and once it does, aquarium water will flood your generator. This will ruin the reaction (other bacteria and organisms in the water will out-compete the yeast) and can make a big mess. So be careful and set the generator down before screwing on the lid and connecting it to the tank.
  
• Finally, a DIY yeast generator is a rather low powered CO2 generator, so diffusing all that CO2 most effectively and stopping leaks is paramount. One leak can make the whole thing not work. A cheap idea for diffusing the CO2 in the tank (called a reactor) is to put the tubing from the generator into the input of a powerhead or canister filter. The impeller will suck up and pulverize the CO2 bubbles, creating a fine mist that will dissolve much faster. Look for an article soon on the different type of CO2 reactors!

DIY CO2 Recipe: Duration vs. Intensity

The second most difficult part about adding a yeast-powered CO2 system to your planted aquarium, after ripping all your hair out trying to find where its leaking (see our article on building your own CO2 generator for step by step instructions on how to avoid this), is to find a recipe that fits your CO2 needs. You can find all kinds of recipes and resources online that tell you to boil containers, add baking soda, use honey, brown sugar, and all sorts of other crazy things. Take it from me: I've tried these and I still keep coming back to a basic recipe and procedure. The main thing to remember is that depending on what proportion you add the ingredients, you will either get very intense CO2 production for a short period of time, or milder CO2 production for a longer period of time. If you add more sugar and yeast, the CO2 production will be more intense, while adding less of both means it will last longer. This is because as yeast create CO2, they produce alcohol which eventually poisons the yeast and kills it. A smaller amount of sugar and yeast means the whole process is slowed down and lasts much longer. I opt for this type of mix, only because I find it a pain to replace the mixes every week, let alone every few days! My recipe usually produces CO2 at a fairly regular rate for about 14 days. It will continue to produce CO2 for at least another week or so, but it will produce less and less each day. This recipe works well in containers of roughly 2 liters (soda bottles, juice containers):

Ingredients:
2 cups sugar
1 tsp baking soda
1/2 tsp yeast (regular dry baker's yeast is fine, see picture)

• Start with a small cup or bowl and add a small amount of lukewarm water and a pinch or two of sugar. Mix in the yeast with a fork, stirring vigorously until the water is bubbly. This will help to "activate" dry yeast by adding oxygen, preventing mass die-offs that occur if you just dump the yeast into the water. Let this sit while you prepare the container, or for at least 10 minutes, and stir every few minutes to keep the water oxygenated.

• Rinse out your container if you have used it before to remove all traces of alcohol. Fill it about 2/3 of the way with lukewarm water. Tap water is fine.

• Using a funnel, add the 2 cups sugar and the baking soda to the water in the container. If you've used the container before, it's likely you don't have a lid you can use to close it up and shake it, so just put the palm of your hand over the opening and turn it upside down over the sink and shake it gently, making sure to keep the seal with your hand. The point is just to dissolve most of the sugar in the water (otherwise it will just sit on the bottom). If you haven't used the container yet, wait to drill a hole in the lid till after you've shaken it up, just to save yourself a sticky hand.

• If it's been about 10 minutes or longer, pour the yeast and water mixture into the container using a funnel. No need to mix it up, just put the lid on and it should start producing CO2 in anywhere from a few hours (I've had it start in around 1 hour!) to 12 hours depending on how well you activated the yeast.

If you don't have any bubbles after 12 hours, you've probably either got bad yeast or leaks. A leak is much more likely in a DIY setup like this and trust me, it will make you reconsider plunking down $300 for a pressurized CO2 system.

Cheap Lighting for Plants: CF Sprial Bulbs

Cheap, high-output lighting options for smaller aquariums are hard to find. Most are at least $80+ and if you've got a smaller aquarium, it's usually because you don't have the money (or the money for more space) for a larger tank. So, here's a cheaper alternative: Compact Fluorescent Bulbs in an Incandescent Hood. Using CF bulbs, you can put together a lighting unit that can give you up to 50 watts in the space of a 12 inch strip light. The benefits of such a unit are a low cost and comparatively high output and you don't have to buy the bulbs from an overpriced aquarium supplier. For this unit, you need:

• An incandescent strip light - You can use either a full hood like the All Glass Economy Glass Hood (these usually only come in a 10 gallon size) or just the strip light, like this Perfecto Incandescent Strip Light. The benefits of the strip light are that it can be moved and used on any size tank, but it is harder to find in local pet stores and you need to either suspend it (not recommended) or put it on a glass top. It usually costs about $20.

• 2 Full Spectrum Compact Fluorescent Bulbs - You want the screw in variety, not the ones with pins at the base. They also must not be larger in diameter than the light strip they will be used in. Usually, a 25W bulb is about the largest that will fit, unless you can find the non-spiral U-tube variety: then length and the maximum wattage of the strip is the limiting factor (most are 2 x 25W max). These bulbs are quite hard to find in a full spectrum color temperature. Wal-Mart stores often carry a "Lights of America" brand that offers them in Daylight 5500K. Alternatively, many online light bulb sellers, such as 1000bulbs.com or SpecialtyLights.com offer them in spectrums that will work.

There's no altering or assembly required, just screw in the CF bulbs, put it on your tank and off you go! There are a few important things to remember though. Do not expose the bulbs directly to the water. There should be glass or something in between protecting them from water splashes and condensation. Also, the higher wattage bulb you use, the more heat will be generated (more on this below). In a warm climate with no way of cooling the tank, this may cause temperatures to rise to unhealthy levels. This approach certainly offers the most "bang for the buck," but it is not the most efficient means of lighting your tank. Spiral bulbs are less efficient than linear tubes because light exiting the tube has the possibility of reflecting back into another part of the tube, or may just enter another part of the tube directly. This causes light loss and heat buildup and is known as "restrike." So all 50 watts are not entering the tank, but instead some light is being lost in the bulb itself. I haven't been able to figure out or find a figure on just how much light is lost, but it's not so significant that the light output is seriously diminished. The incandescent hoods often don't have any sort of reflector in them (some have a small metal reflector, but it doesn't do much) so some of the light is lost when it is absorbed by the light housing. Regular tin foil can be used to line the housing behind the bulbs which will slightly increase the light getting into the aquarium, but it will block ventilation, causing the bulbs to run much hotter and reducing their life.

If you are looking for the cheapest lighting option with the highest light output, you should consider a CF Spiral bulb unit. Be aware that it is not the most efficent option, many systems are available that offer highly polished and engineered reflectors that give you the same results with a lower wattage because more light is actually getting into the tank. However, these will definitely cost you more up-front.

Pros: Best "bang for your buck" for smaller aquariums, easy to replace bulbs

Cons: Uses more power, creates more heat, less light actually gets into the tank

Total cost: $48: $20 for Incandescent Stip Light, $8 per bulb, $20 for glass hood/canopy