The best way to ensure that you starting with a clean foundation of pure water on which to build your formula of plant-specific nutrients for the perfect nutrient solution is to use water produced by reverse osmosis (RO). This is the only way to guarantee that every single part per million (ppm) of your chosen nutrient formula is being maximized toward plant growth.
Conversely, starting with a base of contaminated tap water with high ppm—made up of all sort of unknown chemical contaminants—obviously does not guarantee the efficacy of your nutrient formula. Nutrient companies use RO water in the manufacture of their product, so they can safely and accurately measure and control their particular formula. These same companies also recommend that their customers do the same.
Additionally, those high ppm of are generally not made up of the best stuff for your plants. Sodium and chloride are often present, as are all sorts of chemical and natural contaminants. Without getting a professional water test, it’s impossible to know what the heck is in there. Characterization of contaminants aside, the amount of ppm alone can present a problem.
For example, say the ppm of your water is 300 straight out of the tap. Maybe your plants are young at this point and only require 600 ppm of nutrient solution. This presents you with a dilemma: Do you add 600 ppm of your nutrient, bringing your total to 900 and potentially damaging your plants with an overly rich solution?
Or, do you only add 300 ppm of nutrient to bring up the whole solution to the recommended 600 ppm level, potentially depriving your plants of 300 ppm of necessary nutrients in order to leave room for the 300 ppm of mystery contaminants in you water? Either way, your formula is far from the perfect balance required for ideal plant growth.
Many people think that the ppm of their water is made up simply of calcium and magnesium, two beneficial minerals that are actually vital to the growth of plants. What these customers don’t realize is that—although calcium and magnesium are necessary and are frequently a major part of ppm—the calcium carbonate and magnesium carbonate present in tap water are generally too large a molecular structure for plant roots to absorb efficiently.
Therefore, these compounds need to be chelated (broken down) into a more usable form. This can be accomplished through fulvic and humic acids, as well as beneficial biologicals; still, these methods require time and energy from the plants—time and energy better spent growing big and strong.
Also, nutrient lock-out—which is when large particles of calcium and magnesium cluster on the roots of plants and prevent other nutrients from being absorbed—is nearly always a result of people using tap water with excessive amounts of calcium and magnesium in addition to plant nutrients that also have calcium and magnesium, creating an imbalance the Ca:Mg ratio.
Some nutrient manufacturers make a hard-water nutrient formula, with decreased levels of Ca and Mg; however, since there’s no way to regulate the specific hardness levels of your tap water (which can fluctuate widely week to week), a hard-water-specific formula seems like a rather unspecific solution.
So, in the end, utilizing RO water and adding plant-specific calcium and magnesium is the best way to ensure fast absorption and assimilation of the substances that ultimately promote explosive plant growth.
The ultimate goal of hydroponics, its mission, its reason for being, is to grow plants as big and as healthy as possible in the smallest amount of time possible. The easiest and fastest way to get the most out of your nutrients is to use the purest water. This in turn can shorten the time needed per harvest, meaning you can get more harvests per year. Experienced gardeners know that reverse osmosis is the best way to get that pure water, and that utilizing pure water means that you’ll be using your feed formula the way that its manufacturer intended.