Passive Hydroponics 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 nutrients and float your plant in the cooler in a piece of styrofoam with a hole for the plant to cut into the middle. This is known as the ‘deepwater culture’ (DWC) of a rafting system. Just be sure not to sink the plant too low or it will drown.
A very simple and effective set up except once a plant grows it will overbalance and sink like a ship in a storm if it is not somehow supported. Still, such a setup may be ideal for something like ‘lettuce’.
Remember the 5 basic requirements plants have to survive? They were light, water, oxygen, temperature, and mineral salts (or nutrient). Keeping these in mind, I would include 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 sounds like the perfect way to grow a vegetable plant…. the 4 basic requirements of plants are met…
The theory is that fish eat and excrete nutrient-rich matter on which a plant will feed and prosper. Will it work? No! You may have some small measure of success by luck alone 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 lily may need. Aquatic plants such as water-lilies have evolved to prosper in such an environment so if you wish to add plants to your aquarium, add aquatic plants, not vegetables.
Another classic ‘passive’ system would be 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. As a finishing touch put a small aquarium bubbler into the jar for oxygen.
A popular and easy hydroponics system is called a ‘wick’ system. Suspend a ‘wick’ made from absorbent material from just under plant roots in substrate down into the nutrient solution. Capillary action will draw nutrient solution up the wick into the growing medium keeping it damp to feed your plants.