Water Quality
The all-important factor in successfully maintaining rainbowfishes in captivity is water quality. Without this, rainbowfishes will not survive for more than a few minutes. Water quality is important to rainbowfishes as air quality is to you and me. Every particle of waste matter in the aquarium will affect the health of your rainbowfishes, and determines not only how well they will live and grow, but also whether or not they survive.
Some water quality factors are more important such as nitrogenous waste levels, dissolved oxygen, pH and temperature. Others, such as alkalinity, hardness, and clarity have some affect, but usually are not significant. Each water quality factor interacts with and influences other parameters, sometimes in complex ways. What may be harmful and cause mortalities in one situation can be harmless in another. Regular testing of your aquarium water and your water source is important and it should allow you to detect and correct problems before your fish are adversely affected. Therefore, knowledge of water testing procedures and interpretation of the results are important for the successful maintenance of rainbowfishes in captivity.
The first consideration is the availability of a good quality water supply to fill the aquarium. Surface water from a natural stream or pond is not recommended as it may contain contaminants, diseases, pests or parasites, any of which may harm the aquarium’s ecosystem. Rainwater drawn from a wellestablished water-tank can be used. However, rainwater is not pure water because it has gases and a range of other particles from the atmosphere dissolved in it, which may include carbon dioxide, oxygen, nitrogen oxides, sulphur dioxide, dust, pollens, bacteria and numerous other compounds. This difference varies with location and proximity to oceans, industry, cities and other contributors.
Using rainwater in the aquarium can have a number of benefits by providing a much more natural source of water for your rainbowfishes. Nevertheless, rainwater should not be used exclusively. Rainwater contains none of the essential trace elements that fish need, and also have no buffering capacity to stabilise the pH. It can however, be mixed with a certain percentage of tapwater. It is possible to produce various water conditions in this manner such as lowering the water hardness or pH of your normal tapwater. If the changes are within the parameters that the fish can adjust to, then suitable conditions can usually be established.
The most common source for water is reticulated (town) water. The domestic water supply of most cities and towns if suitable for human consumption will generally be suitable for use in the aquarium. Therefore, most hobbyists will fill their aquarium with water drawn from the household tap. Nonetheless, municipal water supplies are typically treated with chlorine compounds to control bacteria and make it suitable for drinking. If used for fish keeping, then these compounds must be removed or neutralised with chemicals designed for that purpose. One week of continuous aeration will dechlorinate most household water supplies if the chlorine source is liquid or gaseous chlorine. However, many municipal water supply authorities have switched from using chlorine to chloramine.
Chloramine is a compound formed by mixing ammonia and chlorine in water. Chloramine is very stable and can not be easily driven off, even by heavy aeration. Chloramine is very toxic and high levels can cause all rainbowfishes to die within 24 hours. The actual toxicity will depend on the individual fish, water temperature, and dissolved organic levels in the aquarium water. Most rainbowfishes will exhibit serious signs of stress or die at levels above 0.01 mg/L. Some species are particularly sensitive and will die with even the slightest amount in their water.
It is worthwhile to note here that domestic water supplies often change in character, and must be tested regularly from time to time for contaminants, changes in pH values, etc., using aquarium test kits. It is not uncommon for the level of chloramines in municipal supplies to change drastically, for example, due to some local problem and during that period additional conditioner has to be used. Private water supplies are not consistent in their output either, and should be checked on a regular basis.
Many hobbyists fiddle about with various chemicals or compounds trying to maintain what they regard as natural water conditions, but this often causes more problems than it solves. Duplicating the natural water conditions under which rainbowfishes are found in the wild may seem ideal. However, creating natural water conditions in an aquarium is almost impossible. The natural environment of rainbowfishes is vastly different from that of an aquarium.
Most rainbowfishes live in the tropical and sub-tropical climates of Australia and New Guinea. They occupy virtually every type of freshwater ecosystem, from slow-flowing, acidic, tannin-stained water in coastal swamps and streams to fast flowing clear-water mountain rainforest streams; riverine habitats and their tributaries; lagoons, billabongs and the waterholes of arid desert country. Intermittent streams that are subjected to seasonal or frequent drying are also a common feature in Australian inland waters. As drying proceeds, decreases in water volume concentrate the aquatic life into a reduced area. These isolated pools tend to experience physicochemical extremes in the form of elevated temperatures, fluctuating pH levels and low dissolved oxygen.
The chemistry of natural waters inhabited by rainbowfishes depends on the equilibrium reached with the normal physical, chemical and biological characteristics of the surrounding environment. Water that flows over granite rock will tend to remain soft, low in calcium and bicarbonate. Water flowing over limestone will become alkaline with hardness depending on the amount of dissolved calcium and bicarbonate that it contains. Water with a low pH (<5.0) will dissolve naturally occurring minerals from the soils and rocks. To some extent the water quality will depend on the type of vegetation covering the watershed, since the products of plant decay will find their way into the streams draining the area. Such waters may be clear, or brown with varying amounts of dissolved humic and fulvic acids, formed in the soil through the decomposition of organic matter. Water draining these areas can be acidic, and can be extremely so (down to pH 3.5) with sudden rainfall after a prolonged dry period, leading ultimately to ‘blackwater events’. Documented fish kills from blackwater events are common throughout Australian inland rivers and streams, particularly during extended periods of inundation and prolonged periods of low flow. Therefore, the quality of natural water is never constant; it is constantly changing in response to daily, seasonal and climatic rhythms.
Mention should be made here of the diurnal and seasonal fluctuations of temperature. Changes in water depth and flow rates can affect the rates of diurnal warming and cooling. These physical changes as such, have little effect on the chemical quality of the water. However, they can affect the natural biological community that can live in equilibrium with the particular chemical and physical characteristics of that environment. The natural environment of rainbowfishes is complex, and it is unlikely that they will ever be fully understood. It is not as simple as having the water at a particular temperature or pH. There are so many variables in their natural environment that are either difficult to replicate or are difficult to control in a captive environment. Most rainbowfishes can adapt to these natural fluctuations of water conditions as they occur. All the same, they will not tolerate sudden changes so well. Maintaining a constant stable environment is more important for their long-term survival in captivity. The easiest way to do this is by regular water changes.