Carbon Dioxide (CO2) is an essential nutrient for freshwater aquatic plants. If you are considering bright lights and want faster growing, more vibrant plants, try injecting CO2 in your freshwater aquarium. There are several ways to do this. The most popular is probably by injecting CO2 using a store-bought pressurized CO2 cannister system. Refills are cheap and the setup is low in maintenance. There are also other commercially available implementations that use electricity and carbon blocs. These two methods provide a steady stream of CO2 to your aquarium water.
In this post, I explain a third common alternative, that is, how to make your own CO2 delivery system using cola bottles, yeast, sugar and water. Many hobbyists use this method. This is not a novel idea of mine. I'm just explaining how I put mine together.
A Word of Caution:
I assume you know how to use a drill. If you're underage, please have a parent help you. A DIY system may also inadvertently spill yeast mixture into your aquarium. Experiment carefully and build this at your own risk.
What you'll need:
1. Plastic cola bottles with caps. (I use 1 L (38.8 Fl Oz) bottles.)
2. Airline tubing.
3. Airline check valves.
4. Airline T splitters.
5. Sugar. (Just plain white sugar will do.)
6. Yeast. (I use Red Star Dry Yeast)
7. An air stone or a bubble counter or a reactor chamber. (I'll explain this later.)
8. Epoxy glue. (I prefer J-B Kwik by J-B Weld.)
9. Funnel.
10. Tap water.
11. Tools: A drill, drill bit, sand paper, scissors and a nail or a Q-tip.
How to build the Do-It-Yourself CO2 injector:
STEP 1: First, you must drill a hole in the cap of the plastic pop bottle. This hole will be used to affix an airline valve into the bottle cap. The valve prevents aquarium water from flowing back into the bottle. The bottle cap hole must not be larger than the diameter of the valve's input. In other words, drill a hole that is small enough so that the valve fits tightly.
STEP 2: Sand the cap down a bit to remove plastic roughage left over from the drilling. This sanding also prepares the surface of the cap for epoxy glue.
STEP 3: Prepare the epoxy. Most epoxy glues must be mixed. So mix a small amount with a nail or q-tip on a dry piece of cardboard. Hopefully, you purchased a fast-drying epoxy. The J-B Kwik dries in 4 minutes.
STEP 4: Dab a generous portion of epoxy onto the bottle cap. Do not block off the hole you drilled. Likewise, dab some glue on the underside of the check valve. Insert the check valve in the cap and hold it there tightly for 30 seconds or more. Make sure you glued the valve in such a way that the gas flows OUT of the bottle. If you've glued it upside down, get yourself a new bottle cap and a new valve and start over. Let the cap dry out for half an hour or more. You should repeat the above process for 2 bottles. I'll explain why later.
At this point, you're almost ready to pump CO2 into your aquarium. All
that's left is to create the yeast mixture and assemble the bottle and
tubing.
STEP 5: Grab the plastic pop bottle, the funnel, the sugar and the yeast. Using the funnel, pour one cup or less of sugar into the pop bottle. Then, add 1 teaspoon of yeast.
STEP 6: Fill 3/4 of the bottle with tap water. That is, fill the bottle but leave a couple of inches (5 or 6 CM) of air space at the top of the bottle. Do not shake the mixture. The mixture will expand a little, so do not overfill the bottle because it could cause some of the mixture to overflow into your aquarium, resulting in a disgusting mess.
STEP 7: Cap the bottle with the check valve cap prepared earlier. In the future, remember not to put pressure on the cap itself when removing it off the bottle. Instead, twist the bottle and hold the cap firmly. This way, you will avoid breaking the check valve seal.
STEP 8: Tie one end of the airline tubing to the output of the check valve. Attach another airline to the other bottle you prepared in the same way.
STEP 9: Junction both airlines using the plastic T, so that both bottles send CO2 into one single airline. Tie another airline to the output of the T. This is the final airline that will be sent into the aquarium.
STEP 10: Tie an air stone at the end of the airline tubing and place the air stone in your aquarium. Place the air stone as low as possible, close to the bottom.
That's it. You're done. Within a few hours, the yeast mixture will produce CO2 and you will begin to notice bubbles coming out of the air stone.
Improving the DIY CO2 System:
Now that you've made your own CO2 injection system, here are some tips on improving its efficiency.
Tip #1: Alternate mix replacement. Change the mix in bottle 1 on the first week, then change the mix of bottle 2 on the second week and so on. This is why I showed you how to use 2 bottles instead of 1. This is to keep the CO2 levels balanced on average. The mix in your bottles may last a couple of weeks depending on the type of yeast you use and the amount of mixture you make. So don't change the mix in both bottles at the same time. Alternate.
Tip #2: It is imperative that the CO2 mix thoroughly with the water. Some air stones are quite useless for this. Experiment with different air stones that have smaller holes.
Tip #3: For better performance, use a bubble counter instead of an air stone. A bubble counter is a plastic device that looks like a slalom ladder. The CO2 bubbles are forced to flow slowly through the ladder until they completely dissolve. Nutrafin and others make bubble counters that can be purchased online.
Tip #4: For even better performance, purchase a CO2 reactor. The CO2 reactor replaces the air stone and the bubble counter altogether. It is the most efficient way to mix the CO2 into the aquarium water. There are several models on the market. I use Red Sea's CO2 Reactor 500. This device makes use of a pico pump and a small reactor chamber to create a vortex that thoroughly mixes the gas. The mix is then forced out of the chamber. There are even DIY models too. Search the web.
Tip #5: Experiment with different types of yeast. Some will produce a mix that generates more gas than others. Some will last longer and require less maintenance. There are also chemicals that can extend the life of the mix so that it lasts longer, but I don't remember what those are at time of writing.
Tip #6: You can also buy a yeast-based carbon system from Nutrafin. This avoids the trouble of having to make one yourself.
Tip #7: In case of mix overflow into aquarium, change 70% of aquarium water immediately. Consider putting less water in your DYI bottles to prevent the mixture from expanding too much. Never shake the mix.
I hope you found this post useful.
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