Water Quality Parameters Ppt Download |LINK|
Roshelle Ravenel
Because this system combines plants with animal production, it has a special set of water chemistry requirements, and optimal water quality is essential to a healthy, balanced, functioning system. This guide describes the most important water quality parameters that affect the health and productivity of aquaponics systems. A good understanding of how these parameters interact with each other is necessary in order to maintain a balanced system. For additional information on water chemistry, refer to NMSU Extension Guide W-104, Understanding Water Quality Parameters to Better Manage Your Pond ( _w/W104.pdf)
Selecting the source of water used in an aquaponics system can greatly influence the water quality, and is an important first consideration. Potential sources include well water, municipal water, and surface water. Surface water is not recommended because of the difficulty in ensuring consistency in water quality due to risk of contamination. Municipal water is treated with chlorine and chloramines, which must be removed before it can be used. Whatever source of water is used, it is very important to have it tested and to obtain a water quality profile to ensure that it meets the requirements to grow fish and plants.
Testing frequency will vary depending on the parameter being monitored. However, as a general rule, start-up systems should be tested daily so that adjustments can be made quickly when needed. For example, in response to high ammonia levels, feeding levels can be reduced, aeration can be increased, or water can be diluted. Once nutrient cycles are balanced, weekly testing is usually sufficient.
Warmwater fish (e.g., bass, bluegill, and catfish) require about 5 ppm (ppm or parts per million, which can be used interchangeably with milligrams per liter [mg/L]) and coldwater fish (e.g., trout) require about 6.5 ppm of DO to maintain good health and maximum growth. Tilapia are tolerant of lower levels of DO, but growth rates will be affected. They will come to the surface for oxygen-rich surface water if DO levels go down to 1 ppm. It is recommended that DO levels be maintained at 5 ppm or higher in aquaponics systems. Oxygen levels should be measured frequently in a new system, but once procedures become standardized (e.g., proper fish stocking and feeding rates are determined, sufficient aeration is provided) it will not be necessary to measure DO as often.
Low DO levels are not usually a problem with hobby aquaponics growers with low fish stocking rates. The problem tends to arise more in commercial operations with high stocking rates. If DO levels in your system are too low, increase aeration by adding more air stones or switching to a larger pump. There is no risk of adding too much oxygen; when the water becomes saturated, the extra oxygen will simply disperse into the atmosphere. Dissolved oxygen levels are strongly related to temperature: the warmer the water, the less oxygen it can hold.
Ammonia is the first form of nitrogen released when organic matter decays and is the main nitrogenous waste excreted by most fish and freshwater invertebrates. Ammonia is excreted by fish mainly through the gills and also in trace amounts through urine. Ammonia can exist in two forms: un-ionized (NH3) and ionized (NH4+), also known as ammonium ion. Un-ionized ammonia is extremely toxic to fish, and ionized ammonia is not, except at extremely high levels.
The ratio of NH3 to NH4+ in water at any given time will depend on the pH of the water and the temperature. At pH 7.0 or below, most ammonia (>95%) will be in the non-toxic form (NH4+). This proportion of non-toxic to toxic ammonia will increase greatly as pH increases. Water temperature will also affect the ratio of NH3 to NH4+, with more toxic NH3 present at any given pH in warmer water than in cooler water. For example, at 82F, the percentage of ammonia that is in the toxic form (NH3) is 2% at pH 7.5, compared to 18% when pH is 8.5. The sum of the gaseous toxic form and the non-toxic ionic form of ammonia is called Total Ammonia Nitrogen (TAN). TAN is what most commercial ammonia test kits measure. It is recommended that TAN in aquaponics systems be maintained at
To determine the concentration of un-ionized (toxic) ammonia (NH3) in your water at any given time, multiply total ammonia concentration (TAN) measured in the water by the percentage value given in Table 1 that is closest to the observed temperature and pH of your water sample.
Table 1. Percentage of Total Ammonia Nitrogen (TAN) in Freshwater that is in the Toxic Un-ionized Ammonia Form at different pH values and temperatures (adapted from data presented in Francis-Floyd et al. [2009] and Florida Department of Environmental Protection Chemistry Laboratory Methods Manual [2001])
A biofilter is a place for nitrifying bacteria to colonize. In raft and media-filled bed aquaponics systems, a separate biofilter is sometimes not used because the rafts, media, tank walls, and other surfaces may provide enough area for bacteria to colonize. However, most of the time these systems still use some type of biofilter to help break down organic matter and provide more micronutrients and dissolved CO2 in the water. In NFT (nutrient film technique) style systems a separate biofilter is definitely needed.
Even after your system is fully cycled, it is a good idea to check ammonia levels on a weekly basis to catch changes early and make adjustments before they become big problems. Higher than desired ammonia levels occur when more ammonia is being produced than can be handled by the biofilters. Possible causes for this include overfeeding of fish, fish densities that are too high for the volume of water (a rule of thumb is 1 lb of fish per 2 gallons of water), or not enough aeration. Pumps and DO levels should be checked, and adjustments in feeding rates or fish density should be made.
If plants are not growing, it could be because not enough ammonia is being produced in the system. Enough ammonia must be produced and converted to nitrate in order for the plants in your system to grow. Low ammonia occurs when there are not enough fish or there is too much water for the number of plants being grown. The solution is to add more fish to your system, feed them more, or use a smaller tank.
because both calcium (Ca) and potassium (K) are essential nutrients that must be supplemented in aquaponics systems. Here is the Southwest, water is alkaline and high in calcium content, so adding extra water rather than calcium hydroxide is often sufficient to raise the pH. Failing to measure pH for several days can lead to drops in pH to levels as low as 4.5. At pH 4.5, nitrification has stopped and TAN concentrations can climb to over 30 ppm. When this happens, it is crucial to add base very slowly over several days. Adding a large amount of base all at once will shift the majority of the TAN into the toxic un-ionized form (NH3), and this could kill all the fish.
Occasionally a problem can develop in which the pH does not decline over time but instead remains stable or starts rising. This can be due to something in your system causing pH to rise, such as hard water or other sources of minerals, such as net bags of crushed oyster shells that are sometimes added to systems to stabilize pH and add calcium. Rising or stable pH can also be indicative of anaerobic (oxygen-free) zones in your aquaponics system where denitrification is occurring. Denitrification produces alkalinity and stabilizes pH. To remediate this situation, filter tanks should be cleaned twice a week, and all deposits of organic matter accumulated in the hydroponic section should be removed.
Maintaining a balance between water quality conditions that are optimal for fish, nitrifying bacteria, and plants is crucial to a healthy and productive aquaponics system. By monitoring key water quality parameters such as pH, temperature, and TAN on a regular basis, adjustments can be made in a timely manner to avoid problems and losses in productivity. A variety of kits and meters are available to measure these variables. For most backyard systems, aquarium test kits are adequate. Keep in mind that if your readings exceed the higher ranges, you will need to dilute your test sample. Table 3 provides optimal values for the important water quality parameters in aquaponics systems in general (systems containing either warmwater or coldwater fish) and in tilapia aquaponics systems in particular. Of course, this does not mean that aquaponics systems will not function if values deviate from these ideal levels. Tilapia in particular are very resilient fish that can withstand fluctuations in water quality and poor water quality conditions and still survive. These are simply guidelines to inform growers of optimal conditions to help them make better decisions on how to manage a healthy, functioning system.
Florida Department of Environmental Protection. 2001. Calculation of un-ionized ammonia in fresh water STORET Parameter Code 00619, Revision 2 [Online]. Tallahassee, FL: Chemistry Laboratory Methods Manual. Available at
Klinger-Bowen, R.C., C.S. Tamaru, B.K. Fox, K. McGovern-Hopkins, and R. Howerton. 2011. Testing your aquaponic system water: A comparison of commercial water chemistry methods [Online]. Center for Tropical and Subtropical Aquaculture (CTSA), University of Hawaii, College of Tropical Agriculture and Human Resources. Available at
Rossana Sallenave is an Extension Aquatic Ecology Specialist at New Mexico State University. She earned her Ph.D. at the University of Guelph in Canada. Her research interests include aquatic ecology and ecotoxicology. Her Extension goals are to educate and assist New Mexicans on issues relating to watershed stewardship and aquatic ecosystem health.
This draft technical support document provides recommendations for default values for water quality parameters that can be used in the Freshwater Copper BLM when data are lacking. The document also describes data analysis approaches used to develop these recommendations. Following closure of the public comment period on April 18, 2016, EPA will consider the comments, revise the document, as appropriate, and then publish a final technical support document that will serve as a source of information for states, tribes, territories, and other stakeholders.
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