Organic fertilizers are composite in nature which contains all the natural elements required for the metabolic cycle as well as contains an organic matter and mineral nutrients produced locally. Organic fertilizers comprises a variety of plant derived materials that ranges from fresh or dried plant material to animal manures and litters to agricultural by products.  It enrich the soil and carbonic compounds that are crucial for the growth. There are a lot of advantages of applying organic matter to the pond that improves soil structure, fertility and water holding capacity as well as serves the direct food for certain fish species. But still there are some disadvantages that are summarized below:

The addition of organic fertilizer results in the rapid growth and multiplication of the phytoplankton through bacterial decomposition and release of nutrients that are leached to the pond water. The bacteria and planktons are the food source of the aquatic animals and filter feeders fish. Sometimes, the manure is also directly consumed by coprophagus fish. After the application of organic manure at initial phase Phytoplankton appears and gradually the Zooplankton production is dominant, After each manure application, the nutrient content of the water increases resulting in a planktonic peak. Phytoplankton peak is achieved within 4- days after manure application followed by Zooplankton peak in 5-7 days.

Addition of Organic fertilizer

Digest by Bacteria and Mineralize

Multiplication of bacteria takes place and manure is processed

                           Minerals + CO2                            

Photosynthesis

Phytoplankton

Oxygen production, Feeding of fish on Zooplankton and Phytoplankton

Oxygen pool fish at night when no photosynthesis

Figure 1: Showing the impact of organic fertilizer on aqua pond.

Some of the demerits are enlisted below:

•        Organic fertilizer/ manure are bulk in nature so its very difficult to transport.
•          Continual application of organic matter on the pond will deplete and reduce pond depth.
•          It is hectic time consuming to collect and apply bulk material to ponds on a routine basis
•          There are aesthetic objection and sanitary concern related to the fish produced from manured ponds
•          It is not appropriate for intensive high yield culture systems.
•          The decomposing organic manure creates unhealthy conditions in the pond favoring incidence of some diseases as the gill rot.
•          The organic manure results in unpredictable nutrient quality and high biological oxygen demand which may cause oxygen depletion of pond water when applied at high rates.