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PH (MEASURE OF ACIDITY OR ALKALINITY)

Author : Ena

Update time : 2020-06-10 12:55:36

PH (MEASURE OF ACIDITY OR ALKALINITY)

PH or the concentrations of hydrogen ions (H+) present in pond water is a measure of acidity or alkalinity. The pH scale extends from 0 to 14 with 0 being the most acidic and 14 the most alkaline. PH 7 is a condition of neutrality and routine aquaculture occurs in the range 7.0 to 9.0 (optimum is 7.5 to 8.5). Exceedingly alkaline water (greater than pH 9) is dangerous as ammonia toxicity increases rapidly. At higher temperatures fish are more sensitive to pH changes.
It is an important chemical parameter to consider because it affects the metabolism and other physiological processes of culture organisms. A certain range of pH (pH 6.8 – 8.7) should be maintained for acceptable growth and production. But in semi- intensive culture, re-optimum range is better maintained between pH 7.4 – 8.5. pH 7 is the neutral point and water is acidic below pH 7 and basic above pH 7. pH changes in pond water are mainly influenced by carbon dioxide and ions in equilibrium with it. PH can also be altered by a) Organic acids, these are produced by anaerobic bacteria ("acid formers") from protein, carbohydrates and fat from feed wastes, b) Mineral acids such 7 as sulfuric acid (acid-sulfate soils), which may be washed down from dikes during rains and c) Lime application.
Like DO, a diurnal fluctuation pattern that is associated with the intensity of photosynthesis, occurs for pH. This is because carbon dioxide is required for photosynthesis and accumulates through nighttime respiration. It peaks before dawn and is at its minimum when photosynthesis is intense. All organisms respire and produce Carbon dioxide (CO2) continuously, so that the rate of CO2 production depends on the density of organisms. The rate of CO2 consumption depends on phytoplankton density. Carbon dioxide is acidic and it decreases the pH of water. Also, at lower pH, CO2 becomes the dominant form of carbon and the quantity of bicarbonate and carbonate would decrease. The consumption of CO2 during photosynthesis causes pH to peak in the afternoon and the accumulation of CO2 during dark causes pH to be at its minimum before dawn.
The pH should be monitored before dawn for the low level and in the afternoon for the high level. The magnitude of diurnal fluctuation is dependent upon the density of organisms producing and consuming CO2 and on the buffering capacity of pond water (greater buffer capacity at higher alkalinity). i.e., Diurnal fluctuation of pH is not great in pond water of higher alkalinity. An alkalinity above 20 ppm CaCO3 is preferred in prawn/shrimp ponds. Intervention, such as flushing of ponds to reduce the pH, is advisable when the magnitude of diurnal fluctuation in pH is great.
Nevertheless, one should notice that the drastic fluctuation of pH would cause stress to culture organisms. Normally, it should maintain the daily fluctuation within a range of 0.4 difference. Control of pH is essential for minimizing ammonia and H2S toxicity.

AMMONIA

Ammonia is the second gas of importance in fish culture; its significance to good fish production is overwhelming. High ammonia levels can arise from overfeeding, protein rich, excess feed decays to liberate toxic ammonia gas, which in conjunction with the fishes, excreted ammonia may accumulate to dangerously high levels under certain conditions. Fortunately, ammonia concentrations are partially 'curbed' or 'buffered' by conversion to nontoxic nitrate (No3 -) ion by nitrifying bacteria. Additionally, ammonia is converted from toxic ammonia (NH3) to nontoxic ammonium ion (NH4 +) at pH below 8.0.

HARDNESS

Numerous inorganic (mineral) substances are dissolved in water. Among these, the metals calcium and magnesium, along with their counter ion carbonate (CO3 -2) comprise the basis for the measurement of 'hardness'. Optimum hardness for aquaculture is in the range of 40 to 400 ppm of hardness. Hard waters have the capability of buffering the effects of heavy metals such as copper or zinc which are in general toxic to fish. The hardness is a vital factor in maintaining good pond equilibrium.

TURBIDITY

Water turbidity refers to the quantity of suspended material, which interferes with light penetration in the water column. In prawn ponds, water turbidity can result from planktonic organisms or from suspended clay particles. Turbidity limits light penetration, thereby limiting photosynthesis in the bottom layer. Higher turbidity can cause temperature and DO stratification in prawn ponds.
Planktonic organisms are desirable when not excessive, but suspended clay particles are undesirable. It can cause clogging of gills or direct injury to tissues of prawns. Erosion or the water itself can be the source of small (1-100 nm) colloidal particles responsible for the unwanted turbidity. The particles repel each other due to negative-charges: this can be neutralized by electrolytes resulting in coagulation. It is reported that alum and ferric sulfate are more effective than hydrated lime and gypsum in removing clay turbidity. Both alum and gypsum have acid reactions and can depress pH and total alkalinity, so the simultaneous application of lime is recommended to maintain the suitable range of pH. Treatment rates depend on the type of soil.

REDOX POTENTIAL (OXIDATION-REDUCTION EH)

Redox Potential is an index indicating the status of oxidation or reduction. It is correlated with chemical substances, such as O2, CO2 and mineral composed of aerobic layer, whereas H2S, CO2, NH3, H2SO4 and others comprise of anaerobic layer. Microorganisms are correlated with the status of oxidation or reduction. With the degree of Eh, it is indicative of one of the parameters that show the supporting ability of water and soil to the prawn biomass.
In semi intensive culture photosynthetic bacteria (PSB) plays an important role through absorption and conversion of organic matter into the minerals and nutrients as a secondary production, compared to the primary production of algal population. PSB exist particularly due to low oxygen level and high intensity of light and can significantly improve the culture environment.

WATER QUALITY MANAGEMENT

Water quality parameters should be monitored to serve as guide for managing a pond so that conditions that can adversely affect the growth of prawns can be avoided. In cases where problems are encountered, these parameters can help in the diagnosis, so a remedy can be formulated. Individual parameters usually do not tell much, but several parameters put together can serve as indicators of dynamic processes occurring in the pond.
The population of phytoplankton and microorganisms are major determinants of the level of oxygen and metabolites in the pond. The diet fluctuation of DO (including its vertical profile), pH and CO2 serve as indicators of their population. Since CO2 is the major factor affecting the dial fluctuation of pH, monitoring pH fluctuation may be adequate. Also, CO2 is more difficult to measure.
Daily measurements are conducted at early hours i.e. 5-6 am and after noon measurements in the i.e. 2-3 pm. This represents the period before the start of photosynthesis and the peak of photosynthesis, respectively. Thus the maximal and the minima of these parameters occur during this period. The other parameters do not have a distinct dial pattern and therefore can be monitored only once a day, preferable at a common time. Feed and growth data need to be presented with water quality parameters, side by side. This is because algal blooms are consequences of nutrients from feeds and excess feed can cause the rapid deterioration of water quality.
Careful monitoring and data collection will remain useless unless it influences decisions regarding water management. This becomes more important as cost to implement various management schemes (aeration, water exchange, inputs) increase.
Most of the water quality problems can be solved with adequate water exchange. Thus, if large quantities of water suitable for aquaculture were available, monitoring would not be as critical and high production levels can be targeted. If water is limited, the risk of encountering water quality and disease problems increases as one goes for more intensive culture.
The benefits of Nano-Tube aeration technology include a major reduction in energy costs, significantly higher oxygen transfer rates per hour, higher dissolved oxygen (DO) levels, and an improved bottom line.
Nano-Tube aeration technology has been used successfully with a wide range of Aquaculture species and production systems. Whether you are producing shrimp or fish, anywhere you are using traditional aeration systems to oxygenate your water, you can benefit from the efficiency and durability of an Nano-Tube aeration system. Nano-Tube technology has numerous applications including grow out ponds, raceways, recirculating systems, hatcheries, biofloc, cage culture and live-haul trucks, …

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