Aquarium Plants

You can cobble together a system out of individually purchased parts for about $150.00 or you can purchase a complete aquarium specific ready to go system for $300.00. If choosing the latter you can skip most of the following.

You will need to buy the following parts:

1. CO2 Tank (5lb., 10lb., or 20lb.)
2. Dual gauge CO2 regulator
3. Needle valve
4. Silicon airline tubing
5. CO2 reactor (can be DIY built)
   

Plus optional parts:

1. Bubble Counter
2. Check Valves

The CO2 tank is the same used for welding, beer taps, and soda fountains. The usual choices are 5lb., 10lb., and 20 lb. tanks. My preference is for a 10lb. tank. It obviously last twice as long as a 5lb., but it is not much larger in physical dimensions. You can purchase new or get a used exchange tank from a welding supply company much like using propane gas tanks from convenience stores. When your tank becomes empty you simply return it to the welding shop where they exchange it for a full tank. The "deposit" is usually slightly cheaper than a new tank. Figure $50 to $75 for a 5 or 10lb tank. The knob at the top of the CO2 tank is the main control valve. The CO2 is held in liquid form inside the tank at about 800-1000psi. In order to use the CO2 you need to be able to reduce the pressure so that the liquid returns to a gas and the pressure is reduced to about 1-3psi. This is accomplished with the use of a CO2 regulator. The regulator attach's directly to the CO2 tank. It takes the high pressure (1000psi) and reduces it to a more manageable and lower pressure of 10-30psi. The regulator has two gauges, one for the tank pressure and one for the regulated out flow pressure. The first gauge is used to monitor the tanks contents. As long as there is liquid CO2 within the tank the pressure will remain at or near 800-1000psi, once all the liquid is used, and all that remains is gas, the tank pressure will begin to drop indicating the tank is near empty and in need of a refill. Most people decide to refill when the tank pressure drops to 400-600psi. For a 75g aquarium a 10lb. CO2 tank should last at least 6 months between refills. Returning to the regulator, it reduces the pressure down to 10-30psi, this is still to high for our use. To further reduce the flow we add a needle valve after the regulator to fine tune the out flow to 1-3psi. This equates to a small bubble of CO2 of about 0.5 to 2.0 bubbles per second of CO2. This CO2 needs to be "bubbled" into something that allows the CO2 to efficiently dissolve into the tank water. This unit is called a reactor. A CO2 reactor can be anything that allows greater contact with water to hopefully fully dissolve the bubbles of CO2 being added. CO2 reactors can be DIY built for about $10 that run off the flow of a canister filter or they can be purchased for $30 to $75. Alternately you can use a ceramic diffuser that takes the CO2 bubbles and breaks them into a fine mist that almost full dissolves before reaching the water surface.

Additionally you should purchase silicon tubing for running between the regulator and the aquarium. Also, while not absolutely necessary, a bubble counter is a nice option to install. The bubble counter offers a visual reference for the degree of change you make in the flow of CO2 and it gives a constant visual check of system performance. Bubble counters are a simple DIY build too.

Milwaukee makes a pretty good all in one regulator for about $100. This unit is a dual gauge CO2 regulator with a needle valve, bubble counter, and solenoid already installed. The solenoid can be used to turn on and off the flow of CO2 with either a timer or a pH controller. All you would need is some silicon tubing and a reactor. Some people (myself included) use CO2 resistant tubing though the extra expense may be unnecessary.

When you inject CO2 into your tank some of the CO2 forms carbonic acid. Carbonic acid will lower your pH while the KH remains the same. It’s the differential that determines how much CO2 you have dissolve in your tank. It's best to dissolve enough CO2 in your tank water to drop the pH 0.6 to 1.0. This results in CO2 levels of 15-30ppm...20-30ppm is a better range in my expereince. I try to shot for an ending pH that is a weak acid in the 6.6 to 6.8 range though higher is fine too. If your beginning pH is too low, like 7.4 or below, you'll want to increase your pH slightly so that your ending pH isn't too low. You can add calcium carbonate to increase GH, KH, and pH. Or if you don't want to increase the GH you can add sodium bicarbonate (plain baking soda) to raise the KH and pH only. Most fish will be perfectly fine in a weak acid pH that is that way from carbonic acid. To determine the amount of CO2 in your tank you will need to accurately determine your pH and KH. Those numbers will be compared to a CO2 chart which will indicate the amount of ppm or mg/l of CO2 in your tank water. Note that using phosphate buffers or peat filtering will skew the results of these tests and therefore the CO2 charts. Avoid using phosphate buffers/regulators and peat filtering when injecting CO2.

Here’s a link to the CO2 chart:

http://www.tropica.com/article_fullscreen.asp?type=aquaristic&id=445

Here’s a link to show the individual components:

http://www.brainyday.com/jared/aquarium/discus/co2.htm

Here’s a link for a good DIY external Co2 reactor:

http://www.aquaticscape.com/articles/co2reactor.htm