This may be a rehash of things already covered...
One thing I needed to understand when it came to planted tanks was the 3 way balance of lights, ferts, and carbon. At low light levels, the other two are not that critical for most plants. As light increases, the correct proportions of the other two need to be maintained. If out of proportion, poor plant growth due to nutrient deficiencies and out of control algae can result.
Ferts are provided to the plants in two ways: substrate and water column. Substrate ferts can be in the form of DIY root capsules or commercially available root tablets/pellets. Water column ferts can be liquid (e.g. Seachem line of products) or dry (GLA's PPS-Pro).
Carbon can be provided through the injection of CO2 gas (DIY or Pressurized), via liquid (API CO2 Booster, Seachem Flourish Excel, Metricide/Glutaraldehyde), or a combination of both. A pressurized setup should include a tank, regulator, solenoid, bubble counter, check valve, CO2 tubing, diffuser, drop counter, and CO2 indicator fluid. The latter is a pH based fluid that goes into the drop counter; the drop counter displays colors to indicate indirectly how much CO2 is present in the water.
Hope this helps.
