Pond Water Chemistry


By introducing fish into your pond, you have assumed the responsibility for the care of these creatures. This includes not only feeding them but also providing them with a healthy environment in which they can live and thrive. Partial determination of the quality of this liquid environment can be made through chemical measurements. It seems somewhat ludicrous that some one would spend hundreds or thousands of dollars to build a pond and then add hundreds or thousands of dollars of beautiful Koi but would not buy and learn how to use a ten dollar Nitrite test kit. This doesn't mean that one must test the water every few minutes or even every few days. An established pond with the fish appearing healthy should be checked every month or so. It is only when something out of the ordinary is observed and possibly during seasonal changes when an additional test or two might be needed. A simple test at the right time may prevent a small problem from becoming a catastrophe. When starting up a new pond or bio-converter system, daily tests may be required until the converter comes on line, then weekly for a couple of months until the system has stabilized.

 

Test Kits in Estimated Order of Importance

(Required)

1. pH

2. Ammonia

3. Nitrite

4. Thermometer

(Nice To Have)

5. Alkalinity

6. Salinity

7. Nitrate

8. Dissolved Oxygen

(Probably Not Necessary)

9. Chlorine

10. Hardness

 

Just as when medicinally treating your pond, it is imperative to know the total amount of water in your pond and converter/filter system as accurately as possible. Over treatment or under treatment with chemicals can be equally disastrous. Don't guess on quantities, measure them!

 

Do not confuse the terms water quality and water clarity. Crystal clear water can contain compounds that are deadly to your fish. Green water, caused by excessive phyto plankton growth can actually be beneficial to the fish although not very beneficial to the pond keeper who can't see them. Water clarity can give some indications as to mechanical filtration effectiveness.

 

POND NITROGEN-CYCLE

Nitrogen Cycle

A pond with a biologic converter and filled with Koi is a rather complex, somewhat self-con tained ecological system. Each component of this system requires the other components to survive and prosper. The basic portion of the cycle is shown above. Fish waste and other organic waste is converted by bacteria and fungi to Ammonia compounds. These compounds can be injurious to the fish, but a healthy biologic converter populated with Nitrosomonas bacteria consume these Ammonia compounds and convert them to Nitrites. Unfortunately, the Nitrites are just as toxic to the fish as the Ammonia. Again, the biologic converter comes into play with a population of Nitrobacter bacteria that convert the Nitrites to Nitrates. The Nitrates are basically inert to the fish but usable by plants and algae within the pond. As the plants and algae grow and the Koi eat them, the cycle starts all over again. The Nitrosomonas and Nitrobacter bacteria are called aerobic since they require Oxygen to convert their "food" to energy just like the fish.

 

AMMONIA

Ammonia, NH3, measured in parts per million (ppm), is the first measurement to determine the "health" of the biologic converter. Ammonia should not be detectable in a pond with a "healthy" bio-converter. The ideal and normal measurement of Ammonia is zero. When ammonia is dissolved in water, it is partially ionized depending upon the pH and temperature. The ionized ammonia is called Ammonium and is not toxic to the fish. As the pH drops and the temperature decreases, the ionization and Ammonium increases which decreases the toxicity. As a general guideline for a water temperature of 70°F., most Koi would be expected to tolerate an Ammonia level of 1 ppm if the pH was 7.0, or even as high as 10.0 if the pH was 6.0. At a pH of 8.0, just 0.1 ppm could be dangerous.

 

Test kits are available in two basic types. Both read the total of Ammonia and Ammonium, so without knowing the temperature and pH, the toxicity cannot be determined. Suffice it to say that the only good Ammonia reading is zero. The Nessler method type test normally uses drops with a colormetric chart. The Nessler test detects both free Ammonia/Ammonium and also that chemically bound with anti-Ammonia chemical treatments (more about these later). The Salicylate type test is a dual step, using liquid, pill or powder also with an associated color chart. It takes longer to perform and measures only the free Ammonia/Ammonium. Since only the free Ammonia is harmful to the fish, the Nessler test can be misleading under certain conditions but provides additional information under others. The recommended test kit should be able to detect 0-1 ppm of Ammonia particularly for ponds with normal pH levels above 7.0. A wider range kit, 0 - 5 ppm, would also be useful, particularly for those ponds with a typical pH of under 7.0. An Ammonia test kit is considered to be a requirement for all pond keepers.

 

Effects:

Ammonia tends to block oxygen transfer from the gills to the blood and can cause both immediate and long term gill damage. The mucous producing membranes can be destroyed, reducing both the external slime coat and damaging the internal intestinal surfaces. Fish suffering from Ammonia posioning usually appear sluggish, often at the surface as if gasping for air.

 

Source:

Ammonia is a gas primarily released from the fish gills as a metabolic waste from protein breakdown, with some lesser secondary sources such as bacterial action on solid wastes and urea.

 

Control:
Ammonia is removed by bacterial action in the bio-converter and some is directly assimilated by the algae in the pond. Nitrosonomas bacteria consume the Ammonia and produce Nitrites as a waste product. A significant portion of this bacterial action can occur on the walls of the pond as well as in the bio-converter. Ammonia readings may increase with a sudden increase in bio-converter load until the bacterial colony grows to accept the added material. This can happen following the addition of a large number of new fish to a pond or during the spring as the water temperature increases. Fish activity can often increase faster following a temperature increase than the bacterial action does. A bio-converter that becomes partially obstructed with waste and/or develops channels through the media may operate at a reduced effectiveness that can also cause the Ammona levels to increase.

 

Treatment:
Chemical treatments to counteract Ammonia toxcity are available commercially under various trade names. These treatments, most of which are based on Formaldehyde, form a chemical bond with the Ammonia that prevents it from being harmful to the fish. They do not remove it from the pond. The bio converter does the actual removal. Although most of these products use a dosage of 50 ml per 100 gallons to chemically bind up to 1 ppm of Ammonia, be sure and check the manufacturer's directions before use. Note that Nessler type test kits will still show chemically bound Ammonia to be present until the bio-converter bacteria actually consume it. If a pond has a healthy bio-converter, there is not only no need to treat with Ammonia binding chemical agents, it is better not to use them at all.

 

When Ammonia is detected (assuming a pH of about 7.5):

1. Increase aeration to maximum. Add supplemental air if possible.

2. Stop feeding the fish if detected in an established pond, reduce amount fed by half if starting up a new bio-converter/pond.

3. Check an established pond bio-converter for probable clean out requirement.

4. For an ammonia level of 0.1 ppm, conduct a 10% water change out. For a level of 1.0 ppm, conduct a 25% change out.

CAUTION: If the tap water has a higher pH than that of the pond, adding the replacement water may make the situation worse.
5. Chemically treat for twice the amount of Ammonia measured.

6. Consider transferring fish if the Ammonia level reaches 2.5 ppm.

7. If starting up a new bio-converter/pond, discontinue use of any UV Sterilizers, Ozone Generators, and Foam Fractionators (Protein Skimmers).

8. Retest in 12 to 24 hours.

9. Under Emergency conditions only, consider chemically lowering the pH one-half unit (but not below 6.0).

 

NITRITE

Nitrite, NO2-N, measured in parts per million (ppm), is the second chemical measurement made to determine the "health" of the biologic converter. Nitrite should not be detectable in a pond with a properly functioning bio-converter. Thus the ideal and normal measurement of Nitrite is zero. A low Nitrite reading combined with a significant Ammonia reading indicates the Ammonia- Nitrite biologic converter action is not established, while a low Ammonia reading with a detect able Nitrite reading indicates that the Nitrite-Nitrate bacterial conversion activity is not yet working.. Test kits are available in pill, powder, or droplet forms with color charts. Recom mended test kit range 0 - 4 ppm. A Nitrite test kit is considered to be a requirement for all pond keepers.

 

Source:

Nitrite is produced by the autotrophic Nitrosomonas bacteria combining Oxygen and Ammonia in the bio-converter and to a lesser degree on the walls of the pond. Just as with Ammonia, Nitrite readings may increase with a sudden increase in bio-converter load until the bacterial colony grows to accept the added material. This can happen following the addition of a large number of new fish to a pond or during the spring as the water temperature increases. Fish activity can often increase faster following a temperature increase than the bacterial action does. A bio converter that becomes partially obstructed with waste and/or develops channels through the media may operate at a reduced effectiveness that can also cause the Nitrite levels to increase.

 

Effects:

Nitrite has been termed the invisible killer. The pond water may look great but Nitrite cannot be seen. It can be deadly, particularly to the smaller fish, in concentrations as low as 0.25 ppm. Nitrite damages the nervous system, liver, spleen, and kidneys of the fish. Even lower concentrations over extended periods can cause long term damage. Short term, high intensity, "spikes" which often occur during bio-converter startup may go undetected yet cause problems to develop within the fish months later. A common indication of a fish that has endured a Nitrite spike in the past is that the gill covers may be slightly rolled outward at the edges. They do not close flat against fish's body.

 

Control:
About the only control of Nitrite is through the maintenance of a "healthy" bio-converter. Within the media, Nitrobacter bacteria combine Oxygen with the Nitrite to convert it to the relatively benign Nitrate. The Nitrobacter bacteria receive considerably less energy from this conversion process than do the Nitrosomonas bacteria in the Ammonia to Nitrite process. For this reason, they are not as hardy and tend to be the last to come and the first to go when a problem occurs within the bio-converter. Water change outs can reduce the levels temporarily by the same amount as the percentage of water changed. The addition of salt helps reduce the toxic effects significantly but should only be used as a interim measure, not as an ongoing treatment.

 

Whenever 0.25 ppm of Nitrite or more is detected in a pond:

1. Increase aeration to maximum. For a Nitrite level of 1 ppm or greater, add supplemental air, if possible.
2. Stop feeding the fish if detected in an established pond, reduce amount being fed by half if starting up a new bio-converter/pond.
3. Discontinue use of any UV Sterilizers, Ozone Generators, and Foam Fractionators (Protein Skimmers).
4. For a Nitrite level less than 1 ppm, conduct a 10% water change out and add 1 pound of salt per hundred gallons of changed water.
5. For a level between 1 and 2 ppm, conduct a 25% water change out and add 2 pounds of salt per hundred gallons of changed water.
6. For a level greater than 2 ppm, conduct a 50% water change out and add 3 pounds of salt per hundred gallons of changed water.
7. Retest and repeat above in 24 hours.
8. For Nitrite levels of 4.0 or greater, consider transferring fish.

 

NITRATE

Nitrate, NO3-N, measured in ppm, is the third and last measurement used to determine the "health" of the bio-converter. Nitrate is produced by the autotrophic Nitrobacter bacteria combining Oxygen and Nitrite in the bio-converter and to a lesser degree on the walls of the pond. A zero Nitrate reading, combined with a non-zero Nitrite reading, indicates the Nitrite-Nitrate bacterial converter action is not established. Test kits are available with dual droplet or pill form with color charts. The recommended test kit range 0 - 200 ppm. A Nitrate test kit is considered nice to have but not required for the average pond. In an established pond with part of the routine maintenance including 5% to 10% water change outs every two to four weeks, Nitrate levels will normally stabilize in the 50-100 ppm range. Concentrations from zero to 200 ppm are acceptable.
Where Ammonia and Nitrite were toxic to the fish, Nitrate is essentially harmless. There have been reports that high nitrate levels may weaken the colors in Koi but there have also been reports that high nitrate levels can enhance the colors. Similarly, I have read reports, fortunately not in the same article, that high nitrate levels will both stimulate and suppress spawning activity. If the Nitrate concentration gets too high, the Nitrite-Nitrate converting bacteria (Nitrobacter) may not be able to do their job effectively resulting in a raised Nitrite level. Nitrate is the end result of the nitrification cycle and is very important to plants in their life cycle. This is why the plants in your garden can flourish from being watered with the waste water from your pond (assuming you haven't added too much salt).


Note the large difference in the ranges of the test kits being used to measure Nitrate (200 ppm) as opposed to those for Ammonia and Nitrite (1-4 ppm). Assuming our the bio-converter was converting the equivalent of 1 ppm of Ammonia to the equivalent of 1 ppm of Nitrite to the equivalent of 1 ppm of Nitrate per day, it would take 100 days or over three months, (longer with any water change outs), for the nitrate levels to build up to the 100 ppm level. The Nitrate concentration is controlled naturally through routine water change outs and to a lesser degree through plant/algae consumption.

 

TEMPERATURE

Whether you measure your pond's temperature in degrees Centigrade or degrees Fahrenheit or both, a thermometer is considered a requirement for all ponds. A floating pool or spa thermometer is good. It is recommended that it be floated in the filter/converter system or tied to an easy access point at the edge of the pond. At a slightly higher cost, the electronic indoor/outdoor thermometers on the market (i.e. Radio Shack) provide a continuous digital readout. Just drop the end of the waterproof outdoor probe into the water. (Note: Small floating glass aquarium thermometers have been swallowed by Koi.)

The temperature of the pond normally follows that of its surroundings although with a delay related to the size of the pond. Direct exposure of the pond to open sky can cause larger swings in temperature. Direct sunlight during the day can cause the temperature to rise higher and heat loss on clear nights can cause the temperature to drop lower than shaded ponds. A clear night sky can absorb a large amount of heat from a small pond and actually drive the pond temperature below air temperature.

Events generally happen faster at higher temperatures and in smaller ponds. Over normal temperature ranges, biologic activity doubles for each 10° rise in temperature. The toxicity of Ammonia increases as the temperature rises and the amount of Dissolved Oxygen that the water can hold decreases. Although Koi have been known to survive for limited periods at 100°F and even higher, the mortality rate of fish conditioned to 75°F water increases rapidly above 85°F. Above 80°F, supplemental air may be required. Below 55°F (12°C), Koi stop producing antibodies and at about 45°F (7°C) enter a state similar to hibernation. Bio-converter bacteria reproduction ceases at about 40°F (5°C).

 

Feeding fish versus temperature.

Less than 50°F........Do Not Feed

50°F-60°F.............2-4 times weekly

60°F-85°F.............2-4 times daily

Above 85°F............Do Not Feed

 

In all cases, try to feed only what the fish will normally consume in 10 minutes. Remove any uneaten food within an hour.

Fish do not like changes in their environment of any kind including temperature. Any changes add stress to the fish and the larger and faster the changes, the greater the stress. This is considered by many to be the primary reason that fish do better in larger ponds. Another time that the Koi are subjected to stress from temperature changes is when they are being added to a pond from another location. My recommendation is that if the fish have been bagged for more than two hours, it is better to release them immediately than to subject the fish to the "bad" water in the bag for an additional half-hour. Thirty minutes of floating will prevent a sudden shock if the temperature difference is large, but it will not acclimatize the fish to the new temperature. Actual temperature acclimation of a fish takes several days, similar to us dealing with jet lag. It is not only the temperature the fish needs to be accustomed to but also the pH, hardness, alkalinity, "the taste", etc. of it's new surroundings.

 

Other than providing some shade (summer and winter), little can be done or normally needs to be done to control an outdoor pond's temperature.

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