There are several types of hydroponic growing systems and 2 of them are passive hydroponics systems and container hydroponic systems. Each has advantages and disadvantages when compared to other hydroponic growing systems.
A passive hydroponics system will use some sort of mechanism to suspend a plant allowing the roots to hang into the nutrient solution. This method will be moderately successful with the main disadvantage being, ‘how do you support the plant as it grows?’
A simple system would be to fill a 5 gallon cooler with water, mix in an appropriate amount of hydroponic nutrient and float your plant in the cooler in a piece of styrofoam with a hole for the plant cut into the middle. Just be sure not to sink the plant too low or it will drown. This is a very simple and effective set up except that once a plant grows it will overbalance and sink like a ship in a storm if it is not somehow supported. Still, such a set up may be ideal for growing something like lettuce.
Plants have 5 basic requirements they need to survive: light, water, oxygen, temperature and mineral salts (or nutrient). Keeping these in mind, I suggest including an aquarium air bubbler in the cooler to add oxygen and, of course, a good light source.
Aquaponics can also be classified as a passive hydroponics system. This method uses a working aquarium, with fish, as the container and nutrient solution into which you suspend a plant’s roots. It already has an aquarium bubbler supplying oxygen and with a good light source this sounds like the perfect way to grow a vegetable plant. The system meets 4 of the basic requirements of plants. The last (nutrients) are provided under the theory that the fish eat and excrete nutrient-rich matter on which a plant will feed and prosper.
At the hobby level you may have some small measure of success but this is not a viable hydroponics method. Remember that a vegetable plant has evolved to have very specific nutritional requirements – certainly different from the nutrition a water lilly may need. Aquatic plants such as water-lillies have evolved to prosper in such an environment so if you wish to add plants to your aquarium, add aquatic plants, not vegetables. It should be noted that more success is being enjoyed in larger, more regulated aquaponic systems that also double as small scale fish farms.
Another classic passive system is to fill a jar with nutrient solution, jam the neck with a wad of cotton with a small plant poking through with roots dangling in the water. Then as a finishing touch you can place a small aquarium bubbler into the jar for oxygen.
Container hydroponics systems are small vessels holding a growing medium and one or more plants, such as a tomato plant in a bucket filled with pebble stone or a small plant in a flower pot placed in some kind of growth medium (more on growing mediums later).
This pot is periodically flooded with aerated nutrient solution and drained. This flooding can be manual or part of a more elaborate set up involving a pump and timer – although this would probably be classified as an ‘ebb and flow’ system. Therefore the container must have a means to drain the nutrient solution when needed such as a spigot or simply a hole in the bottom of the vessel. These types of container hydroponics systems are generally the simplest of all the types of growing systems.
One simple container system method is to place a tomato plant in a bucket filled with pea stone. The bucket has a spigot near the bottom that can be turned off and on. This bucket is then placed on a support 2 feet off the ground and has a hose attached to the spigot going into a second bucket containing nutrient solution (this bucket is on the ground).
Twice a day, dump the nutrient solution from bucket #2 into bucket #1, with its spigot turned off, until the nutrient solution level reaches the top of the pea stone. Wait a half hour or so and open the spigot to drain the solution back into bucket #2. This is a nice-and-easy manual system guaranteed to be successful.
This system also satisfies the 5 basic plant requirements. Mineral salts are the nutrient which is dissolved into the water. The plant is outside receiving a good light source (and good temperature, hopefully) and the action of dumping the solution into the plant bucket produces oxygen that is carried to the roots. Perfect!
Larry Maki is an avid, self-taught hydroponics gardener from Connecticut with a passion for alternative types of gardening.