Apart from the hassle of mixing the sugar/yeast/water solution and the strong odors it produces, the yeast reactor is inconsistent and will only produce strong CO2 output for a short while. Although many beautiful planted tanks have been maintained with Yeast CO2, eventually the hobbyist will want to move towards a pressurized CO2 system.
The downside to a pressurized CO2 system is initial cost. Most aquarium shops sell complete kits in the $150-$400 range with just the bare essential equipment. With a little bit of knowledge, some searching and a little bit of elbow grease, the hobbyist can easily build a pressurized CO2 system for less than $100.
Below are the components needed:
CO2 Cylinder: Carbon Dioxide cylinders are responsible for holding the CO2 and are used in several industries. Two of the most popular are in welding and the beverage industry. The simplest and most economical way to obtain a CO2 cylinder is to call your local welding supply or beverage distributor. You can find CO2 Cylinders in many sizes from a tiny 2.5 lb to 20lb monsters and even higher. You need to choose a cylinder that will fit under your stand or next to it. A 10lb cylinder fits under most stands, but the most popular size is the 5 lb.
I went to www.infospace.com and searched for "welding supply" and called a half dozen suppliers in minutes. I found a supplier that had a 5lb cylinder for $35. When I went to pick it up, much to my surprise, it was an aluminum cylinder and not the conventional steel. While your cylinder may not be aluminum, they are desireable because they won't rust and are quite a bit lighter to carry around. When my cylinder is empty, all I need to do is bring it back and exchange it for another for a $6.50 fee.
Cost so far:$35 (plus tax)
Pressure Regulator: The pressure in a CO2 cylinder is very high (around 1000 psi when full) so you need something to reduce that pressure to more useable levels for an aquarium. A dual gauge regulator is ideal. One gauge reads bottle pressure and warns you when the bottle is almost empty. The other gauge reads the user-set pressure you adjust with a knob.
I got my gauge on Ebay through www.beveragefactory.com . It is designed for use with a beer keg, and even has a pressure release valve when bottle pressure drops below a level that the regulator can control to prevent dumping all that residual CO2 in the tank at once. Dual Gauge regulators regularly go for around $35 on Ebay.
Cost so far: $70
Needle Valve: Technically, you've got just about everything you need to inject CO2 gas into your tank right now. The shut-off ball valve on the regulator is actually capable of reducing output to about 2-3 bubbles per second, but a finer degree of control is necessary to prevent drastic pH changes.
A Clippard Minimatic needle valve is very popular due to it's great price and excellent fine control. You can buy it directly from Clippard here:
Clippard MNV-4K2 needle valve.
If there is a distributor near you, you can save $10-$20 on shipping and handling. The cost of the valve itself is $10.10 (Marine Monsters sells it for $22 plus shipping).
Cost so far: $80
Bubble Counter: This device is not absolutely necessary, but is useful in fine tuning CO2 delivery rates. They generally run for $10-$20 but I made one out of a small glass spice bottle I had sitting around. I drilled two holes in the top, epoxied two airline fittings in place and ran a tube inside. The air comes through the tube, rises through a level of water and comes out the other airline fitting.
Cost so far: $80 ($100 with purchased counter)
CO2 diffusion Reactor: There are many ways you can diffuse the CO2 gas into your water column. The easiest is to simply run an airline to the inlet of a power filter or powerhead and allow it to shop the gas bubbles into tiny pieces which then dissolve in the water. A good deal of the bubbles will rise to the surface and be lost, though, so a more efficient reactor is desired to help prevent you having to run to refill the CO2 cylinder every month!
If you have a canister filter, you may be able to inject the gas directly into the inlet and allow the impeller to break up the CO2, allowing it to dissolve in the filter chamber. Some filters (such as my Fluval) will not allow this since the impeller allows the gases to collect and cause airlock.
An internal reactor is simple, and there are many plans on the internet. Check out the DIY reactor article for instructions on how to construct your own.
External reactors are a tiny bit more complicated but do the same job. Click here for instruction on how to build one. Both internal and external reactors can be purchased from online retailers.
Additional Cost: $0-$50
Although prices will vary, it's easy to see that you can put together a quality CO2 system for around $80, as I did. The difference in plant growth is astounding as I was only able to maintain CO2 levels of around 15-20ppm with the Yeast/Sugar method. Ideal levels are around 25-30ppm and I am easily able to set the delivery rate to achieve this balance.
Article was written by and pictures are property of Gulfcoastaquarian
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