6.7. Components and how they work - Part 03

Wed, 09/19/2012 - 17:45 -- klm-admin

Surface aquaponics:

Photo: Surface aquaponics planted with water spinach. Circles of white balls are plastic floats. Plants sit on a matrix of bamboo floating just below surface. Palace of Dr. Sun-Yat-Sen, Nanjing China.

Most people confuse surface aquaponics with hydroponics. The technologies have similarities but the structure is different. By using for example styrofoam frames it is possible to grow ornamental flowers directly on fish pond surfaces. Numerous types of soil-based plants also grow on water surfaces if they receive the right combination of nutrients and the right support on floatation devices.

Fish only eat part of the roots and this does not seem to harm growth of the plants. This allows up to 35 percent of the pond surface space for agricultural production without harming oxygenation processes in the ponds.


Ducks produce eggs, meat, recycle nutrients in ponds and eliminate insect larvae. They are kept in a fenced area at the ponds. They eat weeds growing on pond dykes, algae and duckweed which grow in ponds, plus insect larvae at pond edges. They leave their manure in the ponds, which is mineralized and add to the internal pond feed production for fish.

It is not necessary to feed ducks with prepared feed. If this is done, they refuse to eat the larvae and site waste. If ducks are raised from ducklings on available site products, they survive effectively. For more information on poultry consult local agriculture experts, but watch for prejudice in favor of  artificial feed instead of site products. All poultry is tested for parasites and toxins before being taken off the site or consumed.

Photo: Site operator cleaning pigs and flushing wastes into digester. Silva Jardim, Brazil.

Pigs are a time consuming but valuable addition. Each one hectare site supports 3-7 pigs which take about six months to mature. A careful costing decision needs to be made about pigs. It becomes expensive to raise pigs if food has to be brought from off the site. If pig food is raised exclusively on site, then much of the value of vegetables goes to feed pigs.
Local market value of crops versus pig meat needs to be measured. Pigs produce benefits but also require work and investment. The operator needs to evaluate the cost and time of pigs versus other products such as garden crops, fruits from low-maintenance trees, worms, ducks and fish. Pigs produce much manure. A biodigester is required to mineralize wastes before they go into the oxygenation basin.

Optionally it is possible to use manure to feed worms and produce high-protein animal feed.

The garden, pigs, biogas digester and algae pond form a cycle:

  • pigs feed on garden vegetables,
  • manure goes to the digester, producing biogas and nutrients,
  • algae oxygenate treated wastes in algae basins,
  • nutrients are used to grow crops on dykes,
  • crops are fed to pigs until they are grown and slaughtered,
  • by-products are; biogas fuel for cooking or lighting, algae for poultry or human consumption, & sludge for fertilizer.

Pigs require:

  • a constant fresh water supply
  • cleaning with water every day to reduce odors and  keep a constant flow going into the biogas digester.
  • being let out every day to a sunny area

Pig feces need to be tested from time to time for parasites, and  meat inspected by the department of agriculture. Some commercial pig species are particularly sensitive to disease, and so it is a good idea to use pigs which have a higher resistance, but which may produce less meat.

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