Aquatic plants require three main things in order to photosynthesis and flourish: Energy, nutrients and CO2. In an aquarium environment, energy can be provided by via flourescent lighting. Nutrients can be provided by dosing macro and micro nutrients and CO2 via “DIY” or pressurized CO2 systems or naturally. (CO2 naturally diffuses into the water column, along with oxygen). For plants to properly grow, they require all of these things to be properly balanced, or “Houston, we have a problem”. This is especially true if one has excessive lighting, and low CO2 and/or nutrient levels, as these conditions equal algae. As with water chemistry, the key to healthy plants is finding a balance between lighting (energy), nutrients and CO2.
Hobbyist have labeled the different balances low-tech and high-tech. Low-tech (also know as low light) setups utilize low lighting levels, low fertilization levels and (generally) no CO2 injection. High tech (also known as high light) setups utilize high lighting levels, high fertilization levels and pressurized CO2 injection.