The CO2 can be dosed in a few ways. Lowest tech would be to add Flourish Excel (liquid carbon additive), DIY CO2, or pressurized CO2. Remember when you dose CO2 you want to eliminate surface agitation. Don't use air pumps and bubble bars. It's going to do more harm than good for the plants and the plants produce O2, so you don't need alot of air. Liquid would not bee too difficult since your tank is not huge and would not require large amounts. That being said, you could also start out rather inexpensively with DIY CO2. This is basicly a mixture of yeast, sugar and warm water (in precise mixture) in a one or two liter bottle with an air line channeling the CO2 generated by the yeast to your aquarium. You can buy thermal systems at your local pet store or Ebay. The daddy of all CO2 systems are pressurized systems. These systems consist of a CO2 cylinder, regulator, needle valve, and monitor (optional). Some people bubble the CO2 in to their tank by bubbles per second through a bubble counter. This is OK but you have to keep an eye on Ph. If you bubble in too much CO2, you'll have a Ph crash and put a hurt on your fish, even death. A sure fire way to dose pressurized CO2 to your tank would be through a Ph monitor. What this does is watches your Ph level for you and turns on/off your CO2 system when needed. You will need to know the Kh of your tank to set the Ph limit on the meter. Anyway, this was a quick and dirty on the whole thing. Let me know if you have questions. As a personal preference I use pressurized monitored CO2 on both of my tanks (110g and 150g).