Paul Carter

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Nothobranchius sp. Tan97/14

....Nothobranchius seem to thrive in this type of water

As for all fish, water quality is important even though the majority of Killies are very hardy, but this should not be abused by giving them less than ideal conditions. As Killies are normally kept in small volumes of water, which is easy to pollute, frequent water changes will be required to dilute the fish's waste products (mainly nitrates).For most Killies, it is more important to supply stable rather than ideal water conditions (i.e. for the species you wish to keep).

If your fish are feeding and breeding with good colouration then they must be 'happy' with the type of water you are supplying. Only try to change it if they are not doing well. Acclimatise your new fish to your chosen source over a long period of time by slowly adding fresh water to that the fish came in. Many years ago I was shown an excellent method, which is to use strands of wool as a syphon adding fresh water drop by drop. The more strands used the faster the syphon will work. If the size of containers are chosen with care (ie. no chance of overflowing) the syphon can be left to work for many hours without any supervision. Then carry out water changes on a regular basis (eg. 10%-20% per week) to maintain good water quality (nitrates as low as possible - nil would be the ideal).

Types of water

  • Tapwater - Soft/Acid This will be ideal for most Killies, but a pH stabiliser (ie. Waterlife Buffer 6.5) should be added as the acidity can flucuate drastically in the aquarium enviroment without proper buffering. Increasingly these days tapwater is contaminated with 'nitrates' (E.E.C. limit is 50ppm maximum), therefore not a good choice for water changes without pre-treatment by a Nitrate resin (see under Softened Water).
  • Tapwater - Hard/AlkalineThis type of water will be acceptable as long as it is not extremely hard. There are a number of methods to decrease the hardness if the fish are not 'happy', see under 'Types of Treated Water'. Nitrates may still be a problem.
  • Rain Water Excellent as long as it is not contaminated by air-born pollutants. This is why the first part of any rainfall should be discarded. It is good practice to filter all collected water through filter-floss and activated carbon before use. Rainwater is very soft and the pH will need buffering as for 'soft' tapwater. It is advisable to add some tapwater to achieve a hardness of 50 ppm CaCO3 (3 DH) for natural buffering. The amount of tapwater to add will depend on its quality, but 10-20% is normal.

Types of Treated Water

  • Softened Water This is water that has been passed through a single (cation) resin swapping those ions that make water hard (ie. carbonates) for chlorides. The resin is recharged by placing it into a 'rock' salt solution for several hours. The resin can be recharged virtually an indefinite number of times. This method does not affect the amount of 'total dissolved solids' (TDS), therefore the water is relatively stable. Basically this is the same as taking soft water and adding salt, which is sometimes recommended for some species. Personally I have found that Nothobranchius seem to thrive in this type of water, with reduced chance of 'Velvet'. Nitrate resin is only a special type of Softening resin where only the nitrate cation is replaced with chlorides. Recharging is identical.
  • Deionised Water This water has been passed through two types of resin (sometimes mixed) for swapping cations (ie. carbonates, nitrates, chlorides, etc.) and anions (calcium, sodium etc.) for molecules of water. If the resins are not mixed, they may be recharged but require a strong acid and a strong alkali (ie. hydrochloric acid and caustic soda) which are very dangerous to work with. The best option would be to replace the spent resins with fresh. The water is very pure and hence unstable. It must always be buffered and is best mixed with tapwater for natural buffering.
  • Distilled Water This is normally produced by boiling water and condensing the resultant steam. This method needs a lot of energy input and hence is very expensive. The water is very pure and should be treated as for Deionised water. When you defrost the fridge, the water produced is of distilled quality as it has been condensed from the water vapour in the air.
  • Reverse Osmosis Water An excellent method for producing large quantities of pure water. The raw water is forced against a membrane (like a very very fine sieve) which allows the pure water to pass through leaving the impurities behind in a concentrated form as an effluent. The water is again very pure and will need buffering.

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