Exactly as colonel says, the pump breaks up the CO2 into a fine mist, and that is carried to 15 ejection points in the tank. The bar really is almost invisible, with the power head being far more visible than the pipe. Especially when the pipe is located behind and below the plants. I, like many others I'm sure, are disturbed by the mist that's created in the tank, but it really is impossible to stop- after all, one way or the other, if you're using the misting technique, which I believe is the most efficient method, the bubbles, or mist, have to go into the tank; even with an internal reactor, the reactor itself is more visible than this system, and by far less efficient. I have a Madagascar Lace Leaf plant in my tank, and it is saturated with bubbles on the leaf- utterly fantastic display! The pump, I might mention, is one Tom recommended some time ago, which really does the job. The only problem with just using the pump to distribute the CO2 is that the pump's output is quite strong, and blows the plants around far too much- hence the pipe with multiple outlets. I want to add that the pipe is capped on the end with a cap available from the same place as the pipe. Now, if someone can come up with a way to get the bubbles so small that they're invisible, that would be great! But, CO2 is a gas, and I don't see how that can be done. Even my reactor showed some sort of visible display of CO2 injection.
I want to add that I replaced the pump's venturi line and added a 90 degree plastic 1/8" elbow to that line, then reconnected. The original line was bent sharply, creating a situation where it could eventually shut off flow. Not likely, but possible. This elbow was obtained at Auto Zone

Walter, the friendly ole' :gw