aquaponic organic

Aquaponics is the combination of aquaculture and hydroponics. Wastewater from aquaculture systems is recirculated and cleaned by plants. The clean water is returned to the fish and the cycle repeats in a closed loop. In order to maintain the system the only input needed is fish feed and outputs can include, but are not limited to, fish, plants, fruit, prawns, snails, worms, and compost.

Aquaponic systems recirculate aquaculture wastewater into a hydroponic system where the plants remove the 'waste' as fertilizer and return clean water to the fish. High nitrogen water is fed through a series of filters and bio-filters to remove any solids in the water and release gases. The water is then typically pumped into one end of a hydroponic system and drained out the other. For this system to work properly, the amount of fish and plants in a system must be balanced.

For example, if there are too many fish or not enough plants then nitrogenous compounds such as ammonia and will rise to lethal levels. If there are not enough fish or too many plants then plant growth suffers from a lack of nutrients. When these elements are in balance, tremendous growth can be achieved.

This balance is referring to the nitrogen cycle. The nitrogen cycle in aquaponics is the biochemical cycling of nitrogen in the water. Fish waste contains ammonia, which is toxic at high levels. Bacteria convert this ammonia to nitrite and nitrate, which is then more easily taken up by the plants.

Returning to the subject of system components and design, each system must have one or several filters to break down the fish waste. A filter is any type of physical solids filter (sand, sponge, cloth, etc.) that partially or completely removes solids. A bio-filter is one or more of the following: microbes, worms, prawns, and snails. These bio-filters break down organic matter into finer particles, over time creating a source of slow-release fertilizer. A system can have one or the other, or a combination of the two. Actual design and operation often vary greatly from farm to farm.

Deep Water Culture Aquaponic Systems

One of the most common types of commercial aquaponic systems is a deep-water culture (DWC) system. These systems typically operate with a mechanical solids filter to remove fish waste. They are practical for commercial operations because of the simplicity and reliability. The plants are usually grown using foam rafts to support plants in large tanks. Short, vegetative plants are usually grown in this fashion because of the ease of planting and harvesting.

DWC aquaponic systems usually run water from the fish tanks to the filter(s). Once the water is filtered, it can be sent to degassing tanks to remove any carbon dioxide, hydrogen sulfide, or nitrogen gas: CO2, H2S, or N2. After the water is degassed, it is sent to the hydroponic tanks for nutrient removal by the plants. The water spends the majority of its time here before draining to a sump tank.

The sump is a temporary holding spot that mediates the water level of the fish tanks and the hydroponic beds. The sump water is sometimes pumped past a tank where basic chemicals are added to increase the pH when needed since ion removal by the plants has a tendency to lower pH. Water then enters the fish tanks to start the cycle over again.

This is an example of a typical commercial system using mechanical means to oversee production including rearing of fish, filtering of solids, and water quality control. Other systems can rely more on natural filters and operation to create a more diversified ecosystem using worms, prawns, snails, and more.

Flood & Drain Aquaponics - Making the Most of Natural Bio-filters

Flood and drain systems typically rely on bio-filters to remove solids and encase the plant roots in a substrate rather than leaving them in exposed water. The substrate is a sterile medium such as small gravel, sand, or clay pebbles. This provides better support to the plant root than DWC. Flood & drain aquaponics has no sump and all water is stored in the fish tank.

The grow bed is typically placed directly above the fish tank. Water is pumped up into the grow bed to flood the plants. Within the grow bed is an auto-siphon that drains the water once it reaches a predetermined level. The siphon does not use electricity and the system's only electrical requirement is the pump in the fish tank.

Within the grow beds are also typically worms that break down solids into rich slow-release fertilizer. These systems also allow a larger variety of plants to be grown and are often stocked with perennial plants. The gravel medium also provides stronger support for a larger plant.

Plants are also not limited to small, water loving, leafy greens. Many different types of plants can be grown including papaya trees, broccoli, peppers, tomatoes, and much more. This allows the farmer to have a wider variety of produce to sell.

The design of flood & drain aquaponic systems require many individual planting systems for a profitable farm. However, each system can be tailored to the water and nutrient requirements of the plants inside. Some plants require more water than others, so these systems can be timed to provide more or less water for the plants.

Each system can also have a different fish to plant ratio depending on nutrient requirements. Stocking the tanks with more fish will provide more nutrients for growing. So adjusting the amount of fish in the system will affect the nutrient levels for the plants. Plants can be widely diverse, but fish are currently restricted to hardy, fast-growing, freshwater fish.