Carbon dioxide

Carbon dioxide is not obligatory in a planted tank, but if you'd like to get the type of tank that Amano is famous for, it's a necessity. Currently, there are two main methods for doing CO₂: the DIY yeast-sugar-water method and using a CO₂ cylinder.

DIY CO₂

I found DIY CO₂ to be cheap af nd easy (you can get set up in half an hour), but long-term, frustrating and unreliable. It's really just a taste of what's possible with CO₂, but it's a lot more work, and in the long run, it even costs more.

Cylinder CO₂

Needle Valves

My old setup, similar to what I have now

I originally used a DIY needle value setup, similar to the one described here. This setup for the needle value works okay, but you have to use plumber's goop to make the seal tight enough so it doesn't leak. I've set up two of these DIY needle valves, and the problem I had was that one of them worked, and the other was too imprecise. I actually almost killed all the fish in my tank because I couldn't set it accurately enough. The whole point of having a needle valve is to have accurate control of your CO₂, so I recommend spending the extra money, and do it right.

On the advice of the fine folks on the Aquatic Plants Digest mailing list, I purchased a CO2 needle valve (B-SS4 FINE METERING VALVE, 1/4" by Swagelok).

Scott H from APD:

The Swagelock is a very good valve. Not made for shutting a flow off but only for limiting the flow. But it is precise, well made and looks and feels like it, especially when you turn the knob. You mount it on the CO2 line after the regulator and before or after the solenoid, depending on which is easier to do.

You also need to purchase brass inserts for the airline tubing. They don't come with the valve, which can be very confusing, because otherwise it's impossible to set up. The insert is part: B-405-3 Brass Insert for Tubing, 1/4 in. OD - 3/16 in. ID.

The valves used to come in several ways, with different kinds of fittings. Now, the usual is the fitting that requires a small insert in each end of the tubing, which gets squished when the fitting is closed. It's hard to reuse these inserts, so I usually buy a bunch when I need to buy any. They are now 60cents each. Since Swagelock usually sells to commercial outfits/contractors who would have a boxful of these on hand, they don't pack them in with the valves, which is a bummer for folks like us because we don't know we need to order them when we order the valve.

With soft tubing, like vinyl, you need the insert so that, when the nut presses down on the outside of the tubing, the tubing doesn't collapse but instead provides resistance and a good seal. I doubt Homedepot and the like sell inserts alone but Homedepot's universal-compression fittings are usually a kind that come with a similar metal insert for tubing.

To find out how they will charge for shipping you a few inserts, you have to call or use the ask-for-a-quote feature on the web page. Depending on how much Swagelok wants for shipping you a few inserts, it might be cheaper to buy an unneeded fitting at Home Depot just for the inserts. (I went this route, and purchased the Watts A-8, PB96760-PT 1/4" part).

Before you install the valve turn the knob clockwise gently until you can feel it bottom out. Don't close it hard -- this is just to get a feel for what it's like to hit bottom, so to speak. Then turn it back counterclockwise a quarter turn to ensure the the needle inside is *not* bottomed out and won't get damaged during installation if the know gets bumped.

To get everything installed, make sure you note how everything fits when you receive the needle-valve. You want to set it up like it is when you receive it. Also, you may want to use warm, soapy water to get the tubing flexible before installing. It actually took me an hour of frustration before I realized this trick.

Once you have it installed, turn turn the knob again almost all the way down. As soon as it touches or almost bottom, stop, don't force it any farther. Turn your regulator for about 10 psi output and back out the valve until you get the flow you want. You probably will have to go back and forth between the valve and the regulator to get a balanced setting that works. You might end up and 10 psi or 30 psi, depends on your setup, desired flow, and the accuracy of your regulator meter. It's not all that important except that you want to have the metering valve as close to closed as possible and still allow the desired flow. Otherwise, the regulator is controlling the flow and the metering valve is just an expensive ornament.

From then on, you can leave your regulator setting alone and you can fine tune/adjust flow by adjusting the valve in small increments, maybe a 1/16th of a turn at a time.

Leaks

Make sure you check for leaks. I didn't the first time, and had to make another trip to the CO₂ supplier to get some more.

Here's what to do when you have a link:

Chuck Gadd: Check around all the fittings on the tank/ reactor with a solution of liquid dish-soap and water. Just a few drops of soap with 1/2 cup of water, mix it well, and brush it on. You will see bubbles if there is a leak.

Another thing to watch out for: The main valve on the CO2 tank will leak around the valve-stem if the valve isn't completely open, or completely closed.

George: The standard way to check gas lines for leaks is with a soapy solution. You wet the area suspected of leaking and the leaking gas will form bubbles in the soapy water. Sometimes the bubbles are hard to see, so patience and a keen eye are a must.

The most probable leakage point is on the high pressure side, between the cylinder and the regulator or regulator/hose connection. Usually they are far enough from the tank, so that you will not get the soap into your tank.

Of course, there is a commercial liquid product made for that purpose. It is called "leak-detector" or something like that. Your gas supplier might have it. It works muuuuch better than soapy water.

Teflon tape

You can use Teflon tape to improve the seal on the low-pressure side of your regulator (according to Wright), but it's best not to use it on the high-pressure side, as that can lead to explosions in rare cases (according to what I've heard). Scott: The risks with Teflon tape are that it can come apart into very fine pieces, which can then get into and clog fine openings such as you have in metering valves, solenoid valves, and stuff like that.

Some fitters make sure the first few male threads are not taped so that the threads won't push the tap past the female threads -- the threads will hold the Teflon in place.