Study Fish Farming And Learn How To Run Your Own Aquatic Farm
Farming of fish and other aquatic produce is not only increasing in popularity; but also in importance, as natural resources in oceans, lakes and rivers come under pressure. Aquaculture is an industry that has a bright future, and on all accounts is only in it's infancy.
Course Duration: 600 hours
There are six modules in this course, four compulsory, two elective.
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How to Maintain Good Quality Water in an Aquatic Environment
Maintaining each parameter in a balanced state is crucial for keeping the aquarium inhabitants healthy and free from stress. Here are some basic parameters to consider keeping at optimal levels when wanting the organisms to thrive and prosper in an aquarium tank.
Depending on the type of fish inhabiting the aquarium, as well as if it’s a freshwater, brackish water or saltwater tank, temperature will play an important role to help keep a well-balanced ecosystem. Temperature plays other roles in the aquarium ecosystem apart from fish activity, which are also vital to water quality and keeping the biological system in balance. Water temperature, affects the amount of dissolved oxygen which can be held by the water at saturation levels – warmer water holds less DO, while at the same time higher temperatures increase the oxygen requirement by the aquarium ecosystem. Temperature also affects the rate at which the nitrogen cycle progresses, the population turnover and activity of bacteria and other beneficial microbes and the growth rate of aquatic plants, including algae.
Only fish and plant species with similar temperature optimums should be kept in the same aquarium. If temperatures become too low, the fish are likely to become stressed, lethargic and inactive, may fail to feed and become prone to disease outbreaks. If temperatures become to high the oxygen requirement of the fish increase, and they may become hyperactive and nervous.
Hardness is a measure of certain dissolved salts – mostly calcium, magnesium, carbonates and bicarbonates, the harder the water the more of these salts it contains. Hardness is expressed in terms of calcium carbonate content, sometimes expressed as degrees (dH) or as parts per million (ppm - equivalent to mg/l) Water becomes hard when soluble salts dissolve from rock and soil through which it has flowed or percolated.
Soft water contains relatively few minerals, although it is possible to increase the hardness of a soft water supply by adding certain salts. Hard water which requires softening is best treated with reverse osmosis or distillation to remove salts rather than using domestic water softening units which often add sodium to the water. Hard water can also be diluted with a soft water source such as rain water to lower the hardness factor sufficiently for aquarium use.
Hardness and softness in water is assessed by measuring the concentration of dissolved Calcium and Magnesium. Soft water generally contains 0-60 mg/l, moderately hard water 61-120 mg/l, and hard water 121-180 mg/l, very hard water is classified as having over 181 mg/l. Most domestic and well water supplies have some degree of hardness, with an estimated 85% of American water city water supplies being classified as moderately hard or above.
pH is an indicator of the acidity or alkalinity of the aquarium water and it is an important variable for fish health, plant growth, microbial activity and water chemistry. The pH scale runs from 0 to 14, with 0 being extremely acidity and 14 being highly alkaline. A pH of 7 is neutral and most fish originate from waters with a natural pH ranging from 5.5 to 8. The pH scale is logarithmic – so each step up or down the scale is 10 times the previous one, therefore a pH of 5 is ten times more acid than a pH of 6 and 100 times more acidic than a ph of 7. The pH of the initial source water is influenced by factors such as water hardness – the minerals that make water hard usually also make it more alkaline, while organic matter and CO2 have an acidification effect. Soft water is often slightly acid. Aquarists can adjust the pH of the source water for an aquarium using pH up and down chemicals, while pH test kits and electronic meters are used to check pH before adjustment.
Most aquarium fish are intolerant of even slight, but sudden changes in pH and exposure to incorrect pH levels can cause acidosis, alkalosis or pH shock. Long-term exposure to the wrong pH levels for a certain fish species can cause a decline in fish health and increase susceptibility to disease.
Salinity is a measure of the levels of dissolved salts, typically – sodium chloride (NaCl) in the water and it is normally applied more to marine and brackish water aquaria. Salinity is calculated as the total weight of `dry’ salt dissolved in a total of 1000 weight units or parts per thousand (ppt). Seawater typically has a salinity of around 35ppt although can vary slightly.
In aquaria, salinity is measured as specific gravity or relative density at a certain given temperature. The equipment used to measure salinity in marine and brackish water aquariums are either refractometer measuring refractive index or hydrometer measuring buoyancy.
Hydrometers – There are a range of plastic and glass hydrometers which can be used in aquariums for salinity measurement –these work on the principal of buoyancy where the denser the water in which it is immersed, the higher it will float. Density of the water is a function of the amount of salt dissolved in it.
Refractometers – Changes in the concentration of salt in the water affects the refractive index of light and therefore the light entering the refractometer is deflected to varying degrees which can be read from a scale. Refractometers are used in many industries, often to measure sugars or brine (pure sodium chloride solution), so aquarists need to ensure they are using a refractometer calibrated for seawater rather than brine or salt water.
Oxygen (Dissolved Oxygen DO) and Carbon Dioxide CO2
Fish, just like humans, require oxygen for respiration and expire carbon dioxide. Some fish species, particularly those which have originated from oxygen depleted water ways, have the ability to use atmosphere oxygen, however most species kept in aquaria require good levels of dissolved oxygen to always be present in the water. In a planted tank, plants, including algae, take in carbon dioxide when the lights are on in the process of photosynthesis and release oxygen. At night, when plants are not photosynthesizing they absorb oxygen in the process of respiration and give of carbon dioxide. Microbial life in the aquarium including the bacteria involved in the nitrogen cycle, also have a requirement for oxygen, thus the biological oxygen demand of an aquarium supporting a number of different organisms can be high due to the restricted volume and high stocking rates as compared to what would occur in nature.
Oxygen dissolved in the water (DO) mostly originates from the air, although some may come from plants during the daylight hours. This oxygenation occurs at the water's surface where CO2 is also released into the atmosphere. Increasing the surface area of the air/water interface therefore helps with gas exchange and many aquarists achieve this with use of surface aggregation via filters and/or with air pumps producing small bubbles.
The dissolved oxygen content of the aquarium water is not only dependent on the amount of surface agitation but also on water temperature. The warmer the water the less dissolved oxygen it can hold at saturation. Water holds relatively small amounts of dissolved oxygen at saturation – only around 11ppm (parts per million) at 10oC, reducing down to 8ppm at 25oC, thus the aquarium ecosystem is highly dependent on re-oxygenation methods to keep fish healthy.