Tuesday, May 19, 2009

Ammonia is for cleaning, not Koi ponds.

Every week or less I perform water tests on the Koi Garden pond. This test includes three basic tests. Depending on the results of those tests, I might do some additional more extensive testing. I normally do testing with chemical droplets applied to a sample taken from the pond. Depending on the test, up to two different sets of drops may need to be applied along with a regimen of mixing and waiting. The resultant mixture is color compared to key cards included in the tests. Based on the color key, some action may be required: change of water, addition of some chemicals, etc. I am also trying a new type of test I found at Lowes (Lowes.com). It is a strip of paper with the testing mediums for all the tests painted on the each paper. The paper is dipped in the pond water and then reviewed against a key for color changes. The strips include tests for Nitrate and Nitrite, including pH and water hardness. Despite the absence of a direct Ammonia test on these strips, the convenience alone makes them desirable. In the tests I performed, the strips appeared to get the same results as the chemical drops.

Based on these most recent tests, I got some responses that required an action. But before we discuss the failed test, some background is required. The key to the biological filter is the nitrogen cycle. See below for a figure of the nitrogen cycle (diagram below). Ammonia results from the decomposing Koi waste and any other biological matter that gathers and decays in the pond. Beneficial bacteria called Nitrosomonas converts the Ammonia into Nitrites. Nitrites are converted to Nitrates by a different bacteria called Nitrobacter. Additional beneficial bacteria ingest Nitrates to fully clean the water. Knowledge of this nitrogen cycle and the correct interpretation of the test results allow a person to respond correctly to clean your pond.

When I applied this series of tests to the Koi Garden pond, I got an indication of higher levels of Ammonia than were warranted. In new ponds and ponds at the beginning of the warmer season, it is common to see some Ammonia responses on tests. These indications should reduce or go away fairly quickly as the beneficial bacteria grow. It may take up to 4-6 weeks to get all the beneficial bacteria growing in your filters. In my last tests, I had very low Ammonia, and progressively higher Nitrites and Nitrates. This indicates that the biological filter was “moving through the Nitrate cycle”. To have the Ammonia levels increase rather than decrease indicates that the amount of the particular beneficial bacteria was decreasing rather than increasing or remaining stable.

There are two actions that must be taken:
One, immediately reduce the level of Ammonia in the Koi Garden pond; Two, remove the cause of the increase of Ammonia levels.
1) The best way to quickly remove the Ammonia from the pond is partial water changes. Change 20 to 30% of the pond water and replace it with clean water. The addition of salt to the pond water and having a ph outside the range of 6.8-7.5 can both reduce the toxicity of the Ammonia. Salt should not exceed .2% in a pond but in a bath can go to .3%.
2) Removing the cause of the increased Ammonia is a more complex issue. There could be a number of causes for increased Ammonia. A rapid increase in food, sunlight, an increase in degrading biomass in the pond, an increase in the number of Koi in the pond, and a decrease in the number of beneficial bacteria are all possible causes for increases in Ammonia. In the Koi Garden pond, no additional fish or increased food amounts were introduced. I did not think the amount of leaves in the base of the pond were significant enough for the Ammonia I was measuring. I may have inadvertently increased the dead material as an outgrowth of killing the algae. In a future blog, I will write up discussions about adding plants to a pool and also a tool that works as a great cleaning device.

In previous blog entries I had discussed the green water or algae we had in the pond। To counter the algae, I turned the UV filter on. In a few days the green water was gone. The UV light sterilizes any live organic material in the water so it would have killed the algae and it would have dropped to the pond floor or end up in the filter where it would have acted like any other dead organic material. Pond hygiene is a solution to this problem. This could have added to the Ammonia in the pond. The UV filter might have caused the Ammonia situation to be worse in another way as well. The UV light will not only sterilize algae but it will also sterilize beneficial bacteria suspended in the water. Most of the time, beneficial bacteria introduced into a pond will eventually find a home in the filter medium or attach itself to the pond wall. But newly introduced bacteria will remain suspended in the water for a while and will, if it passes through the UV filter, get sterilized by the UV light. If I had not waited enough time after introduction of beneficial bacteria to the time when I turned the UV filter on, I could have reduced the amount of beneficial bacteria. The solution to this would be to turn off the UV filter whenever I introduce beneficial bacteria to the pond.

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