Actually, you could use this method for any aquarium, but it would probably be more worthwhile on a larger aquarium, say 55g and up. It's very simple, and very cheap.
You will need a powerhead with a venturi (a cannister filter would be ok too), some pvc pipe or some rubber tubing (clear is preferred) w/ an endcap, 3 or 4 clippy things with suction cups, a drill, and some CO2.
The pipe or tube will essentially become a spraybar, which will be placed at the bottom rear of the aquarium. Drill some small holes along the length of it, cap it, and hook it up to the powerhead, stick the CO2 line onto the venturi inlet on the powerhead, and BAM--even CO2 distribution with mist!
Here is why this method is superior to most others:
1. There will be no gaudy equipment stinking up the aquaium because everything will be out of sight (if you plant correctly).
2. The powerhead will chop up the CO2 bubbles creating a mist effect, which will rise up through the plants throughout the entire length of the tank. Misting is ideal because CO2 will come into direct physical contact with the plants. More CO2 = better growth.
3. It's cheap. Aside from a powerhead of your choice, this only cost me $3.46.
4. Flexible tubing can be run underneath the substrate if your 'scape so requires it.
5. Better plant growth = less algae.
Pics!
This pic shows the simple connection to the powerhead, a Rio 600, with the CO2 line connected to the venturi. My oto likes it...
This pic shows the endcap (it was free). I've since straigtened out the line. When I replanted, you can't see any of the spraybar or equipment.
Additional Notes:
The Rio 600 (200 gph) seems to be adequate for a 75g, but one size larger should work too. You can adjust pressure by drilling more or larger holes in the tubing, or larger/smaller gauge tubing. I am using .75" tubing (OD) with 10 holes. I would use the RIO 600 for a 55g tank, and possibly one size smaller tubing.