Although it’s just about impossible to keep 100% of these problems out of a hydroponic system, most nutrient solution problems can be easily avoided. Large commercial hydroponic operations usually employ either ozone, UV or chemicals to provide constant disinfection to their nutrient solutions. These are quit impractical for the home hydroponic gardener. A newly planted hydroponic system is very much like a soil garden in that the different microbes will begin to compete with each other, just as they do in the soil. Different species of microbes, bacteria and fungi will begin to dominate, in healthy soil it’s usually the beneficial microbes, bacteria and fungi that dominate most. This keeps the undesirable ones at bay.
Identifying Nutrient Solution Problems
Cloudy nutrients are a clear indicator that something is wrong, as well as what looks like a fur floating on in and on top. These are most likely to be caused by fungi in the nutrient solution. Nutrients can also become cloudy because of bacteria, but bacteria usually causes a slime and/or jelly like mass in the system, it may also have a bad smell. Bad odors tend to be strong, hard to get rid of and are usually a result of bacteria multiplying out of control in the nutrient solution. When bacteria and/or fungi are present in the system they tend to use the oxygen in the nutrient solution that the plants need, this winds up smothering the root systems of the plants. This kills the roots, and when the roots start to die they produce more dead organic material in the system, that perpetuates even more growth of bacteria and fungi as it decomposes.
Microbial growth in the nutrient solution itself is a result of having organic materials somewhere in the system, in order for it to feed on. There are both good (beneficial), and bad (harmful) microbes, most of these are harmful to plants. The beneficial microbes don’t hurt the plants but feed on the harmful microbes. That keeps the harmful ones from growing out of control. The microbes which produce the bad smells, slime and other undesirable problems are not the ones you want to be growing, their growth results in stagnant, oxygen starved nutrient solution, and thus root death. Once the roots begin to die undesirable microbes (known as pathogens) begin to set in, this makes disease control very difficult. They can also clog drippers, emitters, as well as other parts of the system. Cleaning and disinfecting the whole system without damaging the plants will be extremely difficult and time consuming.
The organic mater that these microbes feed on can come from rotting root systems, vegetation from a old previous crops that was not removed, and the growing medium cleaned and sanitized. It can also come from leaves, twigs, flowers, and even stems form the current crop that made it’s way down into the growing medium. Even from leaves, twigs, flowers, stems, dust and dirt from near by plants that made there way into the system, carried by the wind. This organic mater gives the fungi and bacteria a food source, thus results in it’s rapid population growth.
Prevention of Nutrient Solution Problems
Start with a clean, sterilized system and equipment, introduce only healthy seedlings/plants into your hydroponic system, remove any sick plants as soon as you notice them. Use a good quality water source that’s filtered to get rid of pathogens. Change the nutrient solution from time to time to help prevent buildup of unwanted microbes, and flush the system in between changes to help with flushing them from the system and growing medium. Oxygenating the nutrient solution is easy and inhibits non beneficial microbes, while providing much needed dissolved oxygen 
to the nutrient solution. The easiest way to Oxygenate the nutrient solution is by adding an aquarium air pump, and air stones.
Adding beneficial microbes to the nutrient solution can help sway the balance of beneficial/harmful microbes. Researchers have found that having a layer of inert, porous, clay material in the bottom of the nutrient reservoir will help provide a place for the beneficial microbes, bacteria, fungi to breed, colonies and multiply, particularly when you are not using much growing medium in the hydroponic system for them to colonies in.
This article continues: Is your nutrient solution healthy, part 2
