aquaponics - basics

            Aquaponics - Basics

Fish farming in aquaculture 

One part is fish farming or fish keeping in containers or ( - less frequently - ) in open ponds.

Here different species of fish can be kept as needed and as local climate requirements permit.

Frequently cichlids from the genera Tilapia or Oreochromis are used as particularly fast - growing and undemanding fish, e.g. Nile tilapia or Tilapia mariae.

They can be fed with algae or plant food, however in temperate climates additional energy is required for heating the water. 

Plant cultivation in hydroponics

The second part of an aquaponic system consists of growing plants in an inorganic substrate, similar to hydroponics, however, leaving out the pre-produced nutrient solutions used there.

These plants are usually grown in containers or Grow Beds filled with a substrate ( e.g. , expanded - , clay -  , gravel or other substrates ) and are periodically flooded with nutrient-rich water from the fish tank. Cultivation with the nutrient film technique or Deep Water Culture is also possible.

The water overflow is recycled back into the fish tank.

Bacteria as part of the system

The gravel at the bottom of the fish tank and the substrate of the plant container are covered with a biofilm of nitrifying bacteria, which convert the ammonium and ammonia of the fish excretions into nitrates, via the intermediate product nitrite. These nitrates then become available to the plants as nutrients. This is a technical application of the natural nitrogen cycle.

Additional solids from fish excretions or biofilms can be separated via an intermediate settling tank and composted separately. However in systems with media this is rarely necessary because the media per se produce good filtering.

Alternatively, worm composting in the plant substrate is also practiced, in which case the solids are decomposed and kept in the cycle.

Seperation of Solids

An incremental solids from fish waste or biofilms can be separated via an intermediate settling tank and composted separately, this is in systems with medium but rarely necessary because the media per se brings good filtering.
Alternatively, the worm composting is practiced in the plant substrate, in which decompose the solids and can be obtained in the circuit.

Difference to aquaculture

In aquaponic-systems the water must not be exchanged or additionally filtered, since it is refed into the cycle through the described biological treatment processes and made available again for fish farming in the required quality. Thus, the ecological problem of the euttrophication of natural waters due to the unregulated disposal of waste water from aquaculture does not occur. Fresh water must be supplied only for losses due to absorption by the plants, evapotranspiration, or removal of biomass from the system.