Aquaponics Part 1
Aqua-what? (Part 1)
- By BE Sturgeon
In order to grow fresh vegetables at home you need water, seeds, soil and sun…or do you? Well, you certainly need seeds. Growing plants in the dark would not work. Water is a must, but soil? Soil is a complex mixture of minerals, organic matter, and microorganisms. Minerals and organic matter provide the nutrients for the plants and the microorganisms break down dead plant matter for future use. Moist soil is an ecosystem in itself and can be rich or deficient in nutrients.
Consider a “garden” where the soil is absent. This past October I set up an “experimental” hydroponics system (soilless agriculture) in my basement mainly motivated by the fact that I missed fresh veggies from the garden! I had setup a small hydroponics system during graduate school to grow iron-deficient spinach for photosynthesis research, so I had some basic experience. As a chemist, I have no problem “amending” my soils with fertilizers, so it should not come as a surprise that I could find something to put in the water to provide nutrients for my future plants. This “something” turned out to be living fish. Technically, my hydroponics is now called aquaponics.
An aquaponics system aims to be a balanced ecosystem of fish eating food, fish pooping out waste and then the plants using the fish waste as a nutrient. According to Wikipedia®, “plant nutrition” involves three “main” macronutrients: nitrogen (N), phosphorous (P), and potassium (K), three “secondary” macronutrients: calcium (Ca), sulfur (S), and magnesium (Mg), and a collection of trace minerals. All of these minerals can be added directly to the water (hydroponics) or provided via fish (aquaponics).
As a scientist, this “experiment” initiated many questions. What macronutrients are in the fish poop and does this vary with the type of food I feed them? What are the specific nutrient needs of my plants? How many fish do I need for each plant? Like a scientist, not business guy, I decided to just setup a system and gave it a try. This article is the first of a few documenting this experiment.
Like many science experiments, failed outcomes are generally not reported. The fact that I am “reporting” on this topic means that I have had some success growing plants in a soil-less environment in the presence of fish. Do I have all the answers to the above questions? No, but that seldom stops me for giving it a try!
Shown in picture 1 is the basic growing environment (prior to plants) that consists of a tray containing expanded clay pellets, a water inlet, a water outlet and the fish tank with pump. The fish tank is a used 55 gallon drum (once used for cleaning solvents) with a ~100 gallon/hour pond pump and plumbing to move the water from the tank to the water inlet. The water fills the tray containing the pellets until the water level is high enough to overflow back into the fish tank through the water outlet. The water outlet is a syphon setup, meaning that once the water overflows, a syphon is formed and all of the water in the tray is transferred back into the fish tank. This complete removal of the water from the tray is necessary since most plants do not want to have their roots completely submersed in water; removing all the water allows air to return to the root space making sure the water stays well oxygenated.