Many species of warm and cold water fish have adapted to aquaponics systems. The most common fish cultured in aquaponics systems are tilapia, cod, trout, perch, Arctic char and bass. But from all this, indigo thrives. Tilapia is very tolerant of fluctuating water conditions, such as changes in pH, temperature, oxygen and dissolved solids. They are also in high demand — these white-fleshed fish are often sold in markets and restaurants.
What plants grow well in an aquaponics system? It depends on the density of the fish tank and the nutrient content of the fish manure. In general, the best plants to cultivate in an aquaponics system are green vegetables and herbs. The high nitrogen fertilizer produced through fish manure allows the plant to grow lush foliage. So, leafy plants tend to thrive in aquaponics systems. Lettuce, herbs, and leafy greens such as spinach, leeks, bok choy, basil, and watercress have low to moderate nutritional requirements and are usually suitable for aquaponics systems.
Fruit-bearing plants have higher nutrient requirements, and although they do well in an aquaponics system, they need to be housed in a heavily stocked and well-established system. Vegetables such as peppers, cucumbers, and tomatoes can be cultivated in this type of aquaponics system. The only plants that don’t seem to respond either are root crops like potatoes and carrots. Without soil, these plants will be deformed, and difficult to harvest properly.
Apart from plants and fish, another major component of aquaponics is water itself. Nonetheless, carefully monitoring the pH of the water, which determines acidity, is of utmost importance to ensure a level that is safe for fish. Water quality testing equipment is essential to ensure that fish and plants remain healthy. It is also important to monitor dissolved oxygen, carbon dioxide, ammonia, nitrate, nitrite, and chlorine. The density of fish in the tank, the rate at which fish are growing, and the amount of feed given can result in rapid changes in water quality, so careful monitoring is essential. Although the ratio of fish tank water to hydroponic products depends on fish species, fish density, plant species and other factors, a general rule of thumb is a 1:4 ratio of tank content to bottom content. Basically, for every one part water and fish, you will need four parts plants and basic ingredients.
Some aquaponics systems are equipped with biofilters, living materials that naturally filter pollutants from the water and facilitate the conversion of ammonia and other waste products. Another system feeds fish waste directly into a hydroponic vegetable bed. The gravel in the vegetable bed has a bioreactor, a material that helps carry out the chemical processes of living organisms. Gravel does this by removing dissolved solids and providing a place for nitrifying bacteria to convert into plant nutrients.
Want to bring food production to your backyard? Read on to learn how to set up your own aquaponics system.