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Light penetrating water is scattered and absorbed exponentially as it passes downward. The presence of dissolved organic matter and suspended solids further impedes light penetration, and different types of solids absorb different wavelengths. 

The silicon plants take up in silicic acid from water strengthens cell walls. Among the phytoplankton, diatoms particularly need silicon. 

Hydrogen sulfide, which can form in pond bottom sediment, is toxic to aquatic animals because it interferes with reoxidation of cytochrome a3 in respiration. 

Nitrite, an intermediate compound in the oxidation of ammonia nitrogen to nitrate by nitrifying bacteria in soil and water, is considerably more toxic than nitrate. Exposure to nitrite causes gill lesions and edema in the skeletal muscles of fish, and also affects respiration. 

The reliability of trace element analyses reported by custom laboratories cannot be checked by simple techniques, and results may not always be accurate. One should check the reliability of major ion analyses by determining the charge balance and comparing the measured total ion concentration with the total ion concentration estimated from conductivity. 

Farm trials compare new products or methods with practices in current use. Due to aquaculture’s inherent variability, multiple replicate treatments in experimental units that are as similar as possible are required. 

The use of plastic-lined ponds by shrimp farmers can significantly improve production efficiency, support more production cycles per year, and higher mechanical aeration rates and stocking densities. The capital cost of lining ponds can be very significant, so a thorough feasibility analysis is recommended when considering this production tool. 

El uso de estanques con revestimiento de plástico por parte de los productores de camarón puede mejorar significativamente la eficiencia de la producción, soportar más ciclos de producción por año y mayores índices de aireación mecánica y densidades de siembra. 

When aquaculture pond water suddenly warms, gas bubbles can form in the blood of aquatic animals and lead to stress or mortality. 

Evaporation of water from ponds is influenced by solar radiation, air and water temperature, and wind velocity. Control of aquatic plants can yield some reduction. 

To design a settling basin, know the size distribution of particles, estimated rate of inflow and determination of the smallest particle size to be removed. 

The simplest tool for assessing phytoplankton abundance in aquaculture ponds is the Secchi disk. An electronic turbidimeter can be used to measure the amount of light scattered by a water sample. 

Liming materials neutralize acidity and increase pH in pond bottom soil and water. They also react with carbon dioxide to form bicarbonate and release calcium and magnesium, increasing both alkalinity and hardness concentrations in water. 

Although carbon dioxide is not highly toxic, high levels in the blood have many negative physiological consequences. As carbon dioxide increases, higher dissolved oxygen tension is necessary to load hemoglobin with oxygen. 

Although 16.6 million metric tons of carbon are annually buried in aquaculture ponds, estimated carbon emissions for culture species have approached several metric tons of carbon per metric ton of aquaculture product. 

Farm cages should be sited where water quality is good and water velocity is adequate. The size, shape and position of cages should be selected to favor rapid flushing. 

Ponds constructed on sandy or permeable soils are most likely to have high seepage rates. Ponds built in any soil can seep if improperlty constructed. 

Excessive concentrations of trace metals, especially copper, are toxic to phytoplankton and other aquatic plants. The ionic forms of trace metals are toxic to fish and other aquatic animals, but soluble, chelated trace metals are relatively non-toxic.