Alken-Murray logo header - interpreting water test results


1. Alkalinity: This is the sum of components (mainly bicarbonate, carbonate, and hydroxide) in the water that tend to elevate the pH of the water above 4.5. These factors are characteristic of the source of water and the natural processes taking place at any given time. Alkalinity represents the buffering capacity of water and its ability to resist a change in pH. Alken-Murray recommends alkalinity above 75 mg/L to offset acid produced by bacteria nitrifying ammonia.

The acceptable range for most finfish is 20-200 mg/1 (ppm).

CHEMetrics kits recommended K-9810: 10 - 100 ppm & K-9815: 50 - 100 ppm

 2. Ammonia: Ammonia nitrogen (N) is present in variable concentrations in many surface and ground water supplies. A product of microbiological activity, ammonia when found in natural water is regarded as indicative of sanitary pollution.

Ammonia is rapidly oxidized by certain bacteria, in natural water systems, to nitrite and nitrate--a process that requires the presence of dissolved oxygen. Ammonia, being a source of nitrogen is also a nutrient for algae and other forms of plant life and thus contribute to overloading of natural systems and cause pollution.

In fish, ammonia represents the end-product of protein metabolism and what is important is whether it is present in the un-ionized form as free ammonia, NH3, which is toxic to fish (both freshwater and marine) at >0.03 mg/L (ppm), or in the ionized form, NH4+, in which it is innocuous. The relative concentration of each is pH and temperature dependent. The higher the pH, the more of the NH3 will be present. Ammonia can block oxygen transfer in the gills of fish, thereby causing immediate and long term gill damage. Fish suffering from ammonia poisoning will appear sluggish and come to the surface, as if gasping for air. In marine environments, the safe level of NH4+ is between 0.02 and 0.4.

The USEPA recommends a limit of 0.02 ppm as NH3 in freshwater or marine environments. Total ammonia levels, at this limit, can range from 160 ppm at pH 6 and temperature of 5 degrees C to 0.06 ppm at pH 9 and temperature of 25 degrees C.

If large quantities of fish are suddenly added to the water body (such as during stocking), the ammonia level can spike because the natural bacteria that degrade ammonia are slow to reporduce (having a 14 day cycle), so it is best to add a seeding quantity of Alken Clear-Flo 1100 or Alken Clear-Flo 1200 at the same time you add your new fish, to avoid this problem.

CHEMetrics kits recommended: K-1510: 0-1 ppm & 1 - 10 ppm

 3. Carbon Dioxide: Carbon dioxide (CO2) is present in water supplies in the form of a dissolved gas. Typically, surface waters contain less than 10 ppm free carbon dioxide while ground waters may have much higher concentrations. Dissolved in water, CO2 forms carbonic acid which lowers pH.

Aquatic plant life, from phytoplankton to large rooted plants, depends upon carbon dioxide and bicarbonates in water for growth. Of significance for fish is the fact that when the oxygen concentration falls (e.g. through the degradation of organic wastes), the carbon dioxide concentration rises. This increase in carbon dioxide makes it more difficult for fish to use the limited amount of oxygen present. To take in fresh oxygen, fish must first discharge the CO2 in their blood stream, a process which is slowed down considerably when there are high concentrations of CO2 in the water itself. Unfortunately the CHEMetrics test kits do not measure below 10 mg/L, so if you get a reading on this test, you know your water body is in trouble.

The acceptable range of carbon dioxide for most finfish is <2.0 mg/L (ppm).

CHEMetrics kit recommended: K-1910: 10 - 100 ppm

4. Chloride: Chloride is one of the major anions to be found in water and sewage. Its presence in large amounts may be due to natural processes such as the passage of water through natural salt formations in the earth or it may be an indication of pollution from sea water intrusion, industrial or domestic waste or deicing operations. Potable water should not exceed 250 mg/L of chloride. When calcium or magnesium is the cation, up to 1000 mg/L can be tolerated without a salty taste to the water.

CHEMetrics kit recommended: K-2002: 2 - 20 ppm

5. Dissolved Oxygen: Vital to aquatic life, oxygen enters the water by diffusion from the atmosphere or through plant photosynthesis. Actual solubility is directly proportional to the partial pressure in the gas phase, to salt concentration and temperature. The dissolved oxygen level in water is constantly changing and represents a balance between respiration and decomposition that deplete oxygen and photosynthetic activity that increases it. Organic waste may overload a natural system causing a serious depletion of the oxygen supply in the water that in turn leads to fish kills. Likewise, eutrophic waters, that is those rich in nutrients, achieve the same result through causing massive proliferation of algae (algal blooms) whose eventual decomposition uses up the available dissolved oxygen.

Recommended minimum dissolved oxygen levels for fresh water fish are as follows:

warm water fish .......... 5.0 mg/L (ppm)

cold water fish .......... 6.0 mg/L (ppm)

Koi........... 8.0 mg/L (ppm)

Marine fish......5.0 mg/L (ppm)

Marine Shrimp....> 5.0 mg/L (ppm), close to saturation*

* Reference for shrimp is page 124 Marine Shrimp Culture: Principles and Practices edited by Arlo W. Fast & L.James Lester

CHEMetrics kit recommended: K-7510: 0 - 10 ppm & K-7512: 1 - 12 ppm. A dissolved oxygen meter can be used, if calibrated according to manufacturer's instructions. Self-stirring DO probes are easier to work with, if this option is available, but the test kits are often preferred by consumers treating a single pond.

6. Nitrites: Nitrites occur in water as an intermediate product in the biological breakdown of organic nitrogen, being produced either through the oxidation of ammonia or the reduction of nitrate. The presence of large quantities of nitrites is indicative of waste water pollution. The level considered ideal for marine fish is between 0.01 and 0.04 ppm.

Levels exceeding 0.55 mg/L (ppm) nitrite-nitrogen can cause 'brown-blood' disease in finfish.

CHEMetrics kit recommended: K-7002: 0 - 0.4 ppm & 0.4 ppm - 4 ppm

7. Nitrates: Nitrates occur in water as the end product in the biological breakdown of organic nitrogen, being produced through the oxidation of ammonia . Although not particularly toxic to fish, excess nitrates in the water is often used as an indicator of poor water quality. Under anaerobic conditions, such as in the sludge or soil at the botton of a pond, lake or aquarium, denitrification can be used to convert nitrate back to nitrite and from there to nitrogen gas, removing total nitrogen from the aquatic system. In marine environments, levels of 0.1 to 0.2 are considered ideal.

Levels exceeding 50 mg/L (ppm) nitrate-nitrogen are considered unhealthy for lakes.

Levels from 10 mg/l to 40 mg/l indicate poor water in aquariums, depending on the species being raised.

CHEMetrics kit recommenended: K-6902: 0 - 1 ppm & 1 - 5 ppm

For larger, seriously polluted ponds, lakes, etc., also use: K-6902D: 0 - 25 ppm & 25 - 125 ppm

8. pH: By definition, pH is the negative logarithm of the hydrogen ion concentration. It is in effect an "Index" of the amount of hydrogen ion present in a substance and is used to categorize the latter as acid, neutral, or alkaline (basic).

Most natural waters will have pH values from pH 5.0 to pH 8.5 (compare the range in which Alken Clear-Flo products work best: 6.0-8.5). Fresh rain water may have a pH of 5.5 to 6.0. The carbon dioxide produced by respiration of animals and plants in water have the effect of lowering pH. Carbon dioxide and bicarbonate removed from the water by the photosynthetic processes of aquatic plants raises pH. The same processes alter the dissolved oxygen content; oxygen drops during respiration and decomposition; it rises with photosynthetic activity. A pH that is too high is undesirable because free ammonia increases with rising pH.

The acceptable pH range for most finfish and shellfish species is 6.8-8.5

9. Total Hardness: The Total Hardness of a water represents primarily the total concentration of Calcium and Magnesium ions expressed as calcium carbonate. Hardness may range from zero to hundred of parts per million, depending on the origin of the water or the treatment to which the water has been subjected.

Waters containing hardness concentrations of up to 60mg/L (ppm) are referred to as "soft", those containing 120-180 mg/L (ppm) as "hard".

Recommended level: >130 mg/L (ppm)

CHEMetrics kit recommended: K-4502: 2 - 20 ppm & K-452: 20 - 200 ppm

10. Density: The amount of crowding each species of finfish and shellfish will tolerate varies between species. For the majority of finfish, the limit is 0.2 to 0.5 lbs of fish per inch of body length per cubic foot of rearing space. When the tolerable limit is exceeded, fish will exhibit signs of stress including darkening of body color, "clubbing" of gills, fin nipping or loss of tissue between the fin rays and reduced immunity to disease. Shrimp and prawns will also become more susceptible to disease when over-crowded.

Revised 8/25/2006

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  Interpreting Tests - part 3

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