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Carbon dioxide is both a nutrient and a waste product in aquaculture. Some pond managers feel that application of organic matter to provide additional carbon dioxide can reduce pH and control blue-green algae.
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Iron supplementation of pond fertilizers can improve their effectiveness in promoting phytoplankton growth. Ferrous iron in bottom sediment precipitates hydrogen sulfide gas produced by microbial activity.
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Improved feeds and feeding practices increase the proportion of nitrogen recovered in fish and shrimp and lessen the amount of ammonia excreted by the culture animals.
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Management of dissolved oxygen in ponds with static water is difficult, so managers of non-aerated ponds usually limit stocking and feeding rates.
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Ponds constructed where soils contain sulfides can have problems with low pH in culture water. Liming can be an effective emergency measure.
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Outside optimal salinity ranges, aquaculture species have higher feed-conversion ratios, grow at slower rates, become stressed and susceptible to disease, or even die.
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Phosphorus from uneaten feed and feces of culture animals can cause excessive phytoplankton growth and associated degradation of water quality.
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In the water of aquaculture systems, certain bacteria transform potentially toxic ammonia to nontoxic nitrate through nitrification.
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Alkalinity is an index of the capacity of water to neutralize acidity. Hardness represents the sum of calcium and magnesium concentrations. Both values vary greatly in freshwater sources.
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Simple tools can take water and sediment samples to monitor quality variables in aquaculture ponds. Water surface samples provide limited information, while water column sampling delivers more specific data.
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Although pond water samples collected to measure water quality are often held on ice, the values of some common variables in the samples can vary over time.
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Phytoplankton are essential in intensive aquaculture ponds but an excess can result in shallow thermal stratification.
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There are several methods for evaluating water circulation and mixing in aquaculture ponds. Measurements of concentrated salt dispersal can be complex.
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Mechanical water circulation can prevent stratification and provide more dissolved oxygen near pond bottoms. Strong water mixing can also control algae growth.
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In general, lower-intensity pond and cage farming tends to discharge higher overall pollution loads in farm effluents than closed aquaculture systems.
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Space requirements for aquaculture include the culture water area and associated physical culture facilities as well as the land used to raise plant-based feed ingredients.