The health of your pond depends on good water quality. Testing the water is an important step in monitoring the condition of the pond and its inhabitants. Over time, ponds can become contaminated with high chemical toxins, particularly if the ecosystem is newly established or newly changed or if you neglect to maintain your filters.
Ammonia Ammonia in created by decomposing organic debris such as fish waste and uneaten food and is very toxic for fish. Ammonia may be present in two forms, free and ionised. Free ammonia is the most toxic and will cause death in very low concentrations. Problems associated with non - lethal elevated level of ammonia include gill disease, dropsy and finrot. Most test kits measure the total ammonia (free plus ionised). With a properly functioning biological filter, the ammonia level in the pond should be zero or at least be under 0.1 ppm (mg/l). If the level of ammonia is high make a partial water change and either reduce or stop feeding the fish until the levels have fallen to a safe level.
Nitrite Nitrosomonas bacteria in the filter oxidize ammonia into nitrite, which is less toxic than ammonia, but still bad as it inhibits the ability of the blood to carry oxygen. Our pond may experience a nitrite spike if Nitrobacter colony is not sufficient to oxidize it to nitrate. If the level of nitrite is elevated as shown in our test results, we should make partial water change and if necessary add commercial bacteria high in Nitrobacter to the filter.
Nitrate Nitrate is the end product of the nitrifying of the nitrogen cycle. It is mush less toxic for koi than either ammonia or nitrite. Nitrate is absorbed as food and fertilizer for algae and is then reduced into free nitrogen by anaerobic bacteria. An oxygenated, clean pond will not have any anaerobic bacteria present, so nitrate will accumulate in the pond. An algaecide is often used to kill or control the algae of which the growth is encouraged by the presence of the nitrate. Partial water changes usually will flush out the accumulating nitrate.
pH pH indicates the ratio of hydrogen ions to hydroxyl ions on a logarithmic scale from 1 (pure acid) to 14 (pure alkaline). Pure water is 7.0, meaning that there is equal balance of hydrogen ions and hydroxyl ions. Most tap water in Malaysia is around 7.0. Koi do best in water of 7.2 to 8.0. Koi can tolerate a wide range of pH, from 6.5 to 9.0. Even though koi can tolerate extreme of pH there are diseases directly cause by stress. Acidosis is a reaction of fish to acidic condition, in which the fish act highly agitated, with a lot of jumping. Whereas, alkalosis, a reaction to conditions that are too alkaline, will cause the gill and fin to be destroyed. The pH level may be controlled using "pH up" or "pH down" chemicals.
Dissolved Oxygen Dissolved oxygen is usually only a warm weather concern like Malaysia as it is associated with water temperature and algae. The larger the fish the greater the demand for oxygen – continued low levels of dissolved oxygen will lead to stress and potentially kill fish. Even ponds that have been safe for many years can become at risk as fish grow larger and therefore start to demand more oxygen. Algae takes up oxygen at night, and an algae bloom can cause suffocation in large fish and inhabit the oxidation process of nitrifying bacteria. Any dying algae or decaying organic material will also use up oxygen. Testing for the level of dissolved oxygen will determine if the pond has maximum amount of oxygen for a given water temperature. Good aeration using air stones or a waterfall will help promote oxygenation and ensure dissolved oxygen levels remain at the right level.
