How Poor Water Quality Affects The Health Of Your Fish
The main factor in successful koi keeping lies in the maintenance of good water quality. pH, ammonia and nitrite levels in the pond should be checked regularly. However, what is seldom mentioned is the details of how ‘poor water chemistry’ can affect the health of our fish. The most revealing answer usually given is, ‘it causes stress!!’.
Through understanding how a specific substance present in the water can affect the fish's physiology, we can recognise certain behaviour the fish show as a response. With an understanding of good water quality (zero ammonia and nitrite level through biological filtration, and pH maintenance via water changing), this article intends to reveal how some of the biological processes the fish relies on are affected by certain
chemicals naturally present in ponds.
Ammonia - ideal value in pond = zero
This is a major primary cause of health problems in koi. Ammonia is produced from fish wastes, and is excreted from the gills. It is extremely toxic, although its the extent of its toxicity relates to the pH and temperature of the water. In cold water of acid pH the ammonia occurs as NH4+ or ionised ammonia, which is not toxic to fish. Once the pH and/or temperature start to rise the ammonia begins to convert to its toxic form - NH3- unionised or free ammonia. Even very low levels of free ammonia are extremely toxic to fish.
Effects of ammonia poisoning are disturbed osmoregulation (the maintenance of the fish's body salts), as ammonia makes the fish more permeable to water. Ammonia also reduces the oxygen-carrying capacity of the fish's blood and causes gill hyperplasia (excessive growth of new cells at the gills), which further hinders oxygen uptake. Other effects include destruction of mucous membranes, and degradation of the brain and central nervous system. The list of damage cause by ammonia on fish is seemingly endless.
Fish suffering from ammonia poisoning show flicking, gasping, blood streaked fins, eroded body structures. The fish tend to clamp their fins and isolate themselves at the bottom of the pond.
Nitrite - ideal value in pond = zero
Nitrite, produced by the breakdown of waste matter, is extremely toxic to fish due to the effect it has on Haemoglobin, the oxygen carrying agent of koi blood (haemoglobin is also found in human blood). Any nitrite present in the water will convert haemoglobin to methaemoglobin. This is completely incapable of carrying oxygen. Thus the higher the nitrite level in the water the greater the proportion of methaemoglobin in the fish's blood, the lesser the oxygen-carrying capacity of the blood. As the fish can't get enough oxygen, they increase the ventilation rate and gasp at the surface. Methaemaglobinaemia can be recognised
as the blood of the fish turns from vibrant red to a dull brown; this can be seen when examining the gills.
pH - ideal value in pond = 7.0 - 8.0
Koi prefer a pH of between 7.0 and 8.0. Temporary minor fluctuations outside these values cause little harm to the fish, but prolonged exposure to incorrect pH can cause severe health problems to the fish. If the pH of a pond is below 6.0 fish begin to suffer from a condition called acidosis. The acid water causes intense irritation to the fish, and erodes away delicate surfaces such as the gills. This leaves the fish prone to bacterial and fungal infection. Gill erosion also hinders oxygen uptake, causing a condition called Hypoxia - where the koi are basically suffocating. The agent that carries oxygen in koi blood (Haemoglobin) is less efficient in acid water. Acid water can also trigger metal toxicity from copper aluminium or zinc. These metals can be present in the water in an insoluble form, but the drop in pH can cause them to dissolve, thus causing toxicity problems to the fish If the pH of the pond begins to rise much above 9.0 then the fish begin to show symptoms of Alkalosis. Here the fish suffer from marked gill and skin erosion, again leaving them prone to infection. Also any ammonia present will be in its toxic form NH3 (see ammonia).
The behaviour of fish suffering from acidosis and alkalosis is very similar. Rapid large changes in pH cause the fish to become very excitable; they thrash around the pond, gasp at the surface, and may even attempt to jump out of the pond. Slower chronic changes are less noticeable behaviourally. The fish will appear listless, show excess mucus secretion, and succumb to numerous parasitic and bacterial infections.
GH and KH - ideal values in pond = GH of above 10° dH, KH of above 6° dH
Water hardness is determined by the amount of certain dissolved minerals in the water.
The general hardness (GH), measures the total hardness of the water, or the sum total of all these specific dissolved minerals. The carbonate hardness (KH) measures the proportion of these minerals that contribute to the buffer system or alkalinity. It is the KH that is of prime importance to the health of koi as this measures the pond's ability to resist a downward change in pH. All normal koi ponds will show a downward trend in pH over a period of time. This is due to the release of acid compounds in the mud and gravel of the pond. Also, the filter system releases hydrogen ions into the water as ammonia is converted to nitrate,
and this causes the pH to decline. The koi themselves contribute to the acidification of the water as, like us, they release carbon dioxide as they respire. This dissolves in the water as carbonic acid, thus lowering the pH. If this downward trend in pH was left unchecked the fish would begin to suffer acidosis and eventually die. Certain dissolved minerals that contribute to the hardness of the water can counteract this change by ‘absorbing’ the acids, and thus maintaining a steady pH. These minerals make up the buffer system or alkalinity of the pond, and are comprised mainly of carbonates bicarbonates and hydroxides. (The relationship between hardness, pH and alkalinity is complex, and is an article in itself.)
These essential minerals are present to a lesser degree in soft water, leaving the pond very susceptible to pH crashes. However, if the water is too hard the pH will become too high, and the fish will suffer alkalosis.
The buffering salts are not limitless and will eventually be used up, due to the constant acidification of the pond water.
Thus it is essential to replace the hardness of the water by regular small water changes. If your tap water is very soft (a carbonate hardness of below 4 ° dH (equivalent to 71.6 ppm CaCO3 ) it may be wise to add commercial mineral supplement to the pond to increase the KH or buffering capacity.
Chlorine - ideal value in pond = zero
Chlorine is put into our tap water as a disinfectant; however, it is extremely toxic to fish, causing them to panic and attempt to find chlorine-free water. The fish begin to shake nervously, and rapidly lose coloration. The chlorine has an erosive effect on the gill tissue, causing the fish to become listless and weak, and eventually stop ventilating and die. There are many other compounds in tap water which can be harmful to fish (as reviewed in May 99 issue of KOI CARP), and some form of tap water purification is essential, either through dechlorinating and purifying chemicals or tap water filtration.
Don’t reach for the Malachite Green yet!
Often fish kept in water of poor quality can show symptoms that resemble those of fish infected with parasites or bacteria gasping at the surface can be caused by low oxygen levels, ammonia/nitrite poisoning, or a low pH, all factors hindering oxygen uptake at the gills and/or oxygen carriage by the blood flicking/flashing/scratching, can be caused by irritation due to chlorine, ammonia, or extremes of pH red wounds can be bought about due to prolonged exposure to a low or high pH
Thus before applying a disease treatment to the pond it is vital to ensure the water quality is good, and is not the cause of the symptoms you have noticed in your fish.
Conversely, if the water quality is not ideal then the fish can be more predisposed to parasitic and bacterial infection. It is vital to check your water quality whenever your fish are showing unusual behaviour. If the water quality is poor it must be corrected before any parasite treatments are added.
There are many other chemicals dissolved in water that can affect the health of our koi. For example, heavy metals such as lead can enter the pond; copper can dissolve from plumbing fixtures; pesticides can enter from the garden. There has even been a case of arsenic poisoning of koi, the source of the pollutant being pressure-treated wood surrounding the pond. All these examples are, however, very rare.
Those factors mentioned above are significant to every koi pond, no matter how large or small. All koi are susceptible to poisoning from poor water quality. It is up to us to prevent it happening.
This is simple to do through regular water chemistry checks and frequent small water changes.
Good water quality is the key to fish health!!!