Aquaculture ponds

Applicable to the following sanitary systems Single pit system Blackwater treatment system with infiltration Blackwater treatment system with sewerage (Semi-) Centralized treatment system Sewerage system with urine diversion

Inputs Effluent

Application Level Management Level Household: o Household: o Neighbourhood: x Shared: x City: xx Public: xx xx - suitable, x - less suitable, o - not suitable

Description

Aquaculture refers to the controlled cultivation of aquatic plants and animals; this technology sheet refers exclusively to the raising of fish while the following page on Floating Macrophytes addresses the cultivation of plants. Fish can be grown in ponds where they feed on algae and other organisms that grow in the nutrient-rich water. Through feeding, the nutrients from the wastewater are removed and the
fish are eventually harvested for consumption.

Three kinds of aquaculture designs for raising fish exist:

1. fertilization of fish ponds with excreta/sludge;
2. fertilization of fish ponds with effluent; and
   
3. fish grown directly in aerobic ponds.

When introducing nutrients in the form of effluent or sludge it is important to limit the additions such that aerobic conditions are maintained. BOD should not exceed 1g/m2d and oxygen should be at least 4mg/L. Fish introduced to aerobic ponds can effectively reduce algae and help control mosquito populations.

The fish themselves do not dramatically improve the water quality, but because of their economic value they can offset the costs of operating a treatment facility. Under ideal operating conditions, up to 10,000kg/ha of fish can be harvested. If the fish are not acceptable for human consumption, they can be a valuable source of protein for other high-value carnivores (like shrimp) or
converted into fishmeal for pigs and chickens.

Adequacy

A fish pond is only appropriate when there is a sufficient amount of land (or preexisting pond), a source of fresh water and a suitable climate. The water that is used to dilute the waste should not be too warm, and the ammonia levels should be kept low or negligible.

Only fish that are tolerant of low dissolved oxygen levels should be chosen. They should not be carnivores and they should be tolerant to diseases and adverse environmental conditions. Different varieties of carp, milkfish and tilapia have been successful, but the specific choice will depend on local preference and suitability.

This technology is only appropriate for warm or tropical climates with no freezing temperatures, and preferably with high rainfall and minimal evaporation.

Health Aspects/Acceptance

Where there is no other source of readily available protein, this technology may be embraced. The quality and condition of the fish will also influence local acceptance. There may be concern with contamination of the fish, especially during the harvesting, cleaning and preparation of the fish. If it is cooked well it should be safe, but it is advisable to move the fish to a clear-water pond for several weeks before they are harvested for consumption.

Maintenance

The fish need to be harvested when they reach an appropriate age/size. Sometimes after harvesting, the pond should be drained so that (a) it can be desludged and (b) it can be left to dry in the sun for 1 to 2 weeks to destroy any pathogens living on the bottom
or sides of the pond. ^[1]

Pros & Cons

How to build

Costs

References

1. ↑ Tilley, Elizabeth et al, 2008. Compendium of Sanitation Systems and Technologies. Swiss Federal Institute of Aquatic Science and Technology (Eawag). Dübendorf, Switzerland., pp.141-142 ISBN 978-3-906484-44-0