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Keeping and caring for rainbowfishes in captivity is reasonably simple as far as general aquarium conditions are concerned. They are one of the easiest fishes to maintain in captivity. They also possess all the attributes we look for in aquarium fishes. Ease of breeding, hardy, beautiful colours, peaceful disposition and they won't destroy your plants or move the gravel around in your aquarium. They come in a variety of sizes to suit almost any community aquarium. However, maintaining rainbowfishes in an artificial environment such as an aquarium or pond does require certain responsibilities. Rainbowfishes are living beings and require suitable habitat, proper nutrition, and a stress-free existence if they are to grow and remain healthy. A few of the hardier species may survive without any particular effort on your part. However, if you want to be successful keeping rainbowfishes then you must make an effort to learn some basic aquarium principals to maintain and care for them. The all-important factor is water quality. Water quality determines not only how well they will live and grow in aquaria, but also whether or not they survive.
The freshwater environments of Australia and New Guinea contain mostly soft water, but their pH and clarity will vary depending on their sediment content and the terrain over which they flow. Duplicating the natural water conditions under which rainbowfishes are found in the wild may seem ideal. However, this can often cause more problems than it solves. Creating 'natural' water conditions in an aquarium is almost impossible.
Most aquarists will fill their aquarium with city water drawn from the household tap. However, this water has usually been subjected to many changes. If the changes are within the parameters that the fish can adjust to, then suitable conditions can usually be established. The domestic water supply of most cities and towns if suitable for human consumption will generally be suitable for use in the aquarium.
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 city water if the chlorine source is liquid or gaseous chlorine. However, many municipal water supply authorities have switched from using chlorine to chloramine. Chloramine (NH2Cl) is a compound formed by mixing ammonia and chlorine in water. Chlorine worked well as a disinfectant but was believed to be a contributing factor in the formation of cancer causing trihalomethanes. Chloramine is much more stable and does not form trihalomethanes. However, higher levels of chloramine are required to the same job as a lower dose of chlorine. Chloramine is very stable and can not be easily driven off, even by heavy aeration.
Regular dechlorinators; for example, Sodium thiosulphate or carbon filtration will remove the chlorine part of chloramine molecule but leave the ammonia in the water. The remaining ammonia may be taken up by aquatic plants and nitrifying bacteria, or removed by ammonia neutralisers; for example, Zeolite. However, a water conditioner especially formulated for detoxifying ammonia as well as removing chlorine and chloramine, is the preferred method. 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. Goyder River trifasciata are particularly sensitive to chloramine 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.
In captivity 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 tap water is important and it should allow you to detect and correct problems before your fish are adversely affected. Therefore, knowledge of testing procedures and interpretation of the results are important for the successful maintenance of rainbowfishes in captivity.
Rainbowfishes are mid-water to surface swimming fish and require sufficient space to swim. Therefore the size of the aquarium is very important. In a small aquarium they will feel stressed, with resulting disease problems. The surface area of a rainbowfish aquarium is more important than depth as rainbowfishes swim horizontally not vertically. Aquarium width should be at least 45 cm, particularly for the larger species. Many of the 'standard' sized aquariums sold in pet stores are higher than they are wider and are really not the best type of aquarium for their long-term maintenance.
The stocking density, that is the volume of water available to a single fish, can be a significant health factor. Large numbers of fish confined in the relatively small space of the aquarium can often lead to impaired growth and health conditions. This is due to reduced oxygen levels and increased toxic substances such as ammonia and nitrite. Although there are numerous mathematical formulas to calculate the fish holding capacities of aquariums, they are essentially without merit. Start with a very small number of fish and check the water quality using test kits for ammonia, nitrite, and pH. More fish can be added gradually, building up over the months as your aquarium matures, as long as the water quality is not diminished. Ultimately, your own observations and test results should help you determine what is a safe number of fish for your particular set-up. Most important of all, do not add too many fish to the aquarium at the same time.
Fundamental to the success of a thriving aquarium is a stable environment made possible with a regular maintenance program. This includes regular removal of particulate matter (faeces, uneaten food, detritus, etc.). The removal of algae from tank walls, regular cleaning and removal of particulate matter from the filter. By inserting the end of an expanded siphon tube into the gravel, organic wastes can be removed which otherwise might clog the gravel bed. If used correctly, it will remove the accumulated wastes from the gravel without removing any gravel.
Providing and maintaining a suitable biological filtration system, together with regular water changes, will facilitate the removal and detoxification of wastes. Waterchanges provide regular removal of wastes not normally removed by filtration or bacterial decomposition, and restores a stable environment. Weekly waterchanges of between 25-35% should be employed to avoid any major changes in water quality and chemistry. Weekly changes of at least 50% will be required for rainbowfishes maintained at high population densities. No systems exist, despite misleading claims to the contrary, that can replace waterchanges
If you have the desire to learn more about rainbowfishes and expand your hobby, then join an Aquarium Society such as the Australia New Guinea Fishes Association (ANGFA). Membership in ANGFA offers numerous benefits for both the novice and advanced rainbowfish keeper.
© Copyright Adrian R. Tappin
Updated October, 1999.
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