My favorite way to organize thoughts about aquatic plant learning is this: lighting is a skill set, CO2 is a skill set, plant nutrition is a skill set and finally, algae is a fourth skill set the depends somewhat on understanding a fair amount of the earlier skills. I find plants to be a significantly more complicated thing than water chemistry and tank startup topics.
There are some very good articles pinned in the planted section (bearing in mind that "planted tanks" can almost be considered a "whole 'nother hobby" and you won't need all of it to begin with and needn't be intimidated by it)... starting with Aaron's Back To Basics article.
Plants need access to about 17 basic elements to complete their diet. To help organize these, people divide them up into "macro" nutrients and "micro" nutrients. The macro nutrients are N, P and K (Nitrogen, Phosphorus and Potassium) and more of these are needed, whereas most of the other elements are needed in "trace" amounts, thus the "micro" name. A new tank is a very sterile place for plants and is very good a killing them.
Carbon, one of the 17 essential elements plants need, is special because its needed for making simple sugars which will carry energy around the plant to its cells, an ongoing important task. Of course Hydrogen and Oxygen are also needed for this but these are readily available, being parts of water. Carbon, on the other hand, is quite difficult to get into water in sufficient amounts and indeed is something that underwater plants have struggled with throughout evolution. Carbon Dioxide is the most common and best way that Carbon can be delivered to plants and the only two methods of delivering it are either by fermenting sugar/yeast mixtures in "DIY" do-it-yourself bottles, or by using expensive pressurized gas cylinders with regulator equipment on them. Another way to deliver carbon to plants is via some complicated chemicals that we call "liquid carbon." This is quite popular with "low-light" (non high tech, non pressurized) approaches (and is what I do) but in the long term is expensive because you need the chemicals forever and they are somewhat inferior to doing pressurized CO2. DIY CO2 seems like a good option at first but people grow quickly frustrated with it usually.
Anyway, read about lighting, nutrition and substrates and begin weighing the various carbon options and you'll be a long way toward a beginning understanding of aquatic plants!
~~waterdrop~~
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