Keeping an aquarium with Softwater Fish
Soft water has a lower level of calcium salts than those found in hard water. Fresh water is classified as “soft” when its overall hardness is 6 degrees or less. The hardness of your local tap water can be measured quickly and accurately using one of the many available hardness test kits.
soften the water
If you have hard water, there are ways and means you can soften the water in your aquarium. Firstly, a ‘ softening pillow ‘ can be placed inside your filter. These resemble large ‘tea bags’ that work by allowing water to pass over an ion exchange resin and can be recharged with aquarium salt so can be used over and over again.
In the beginning, the softening pillow will need to be recharged quite often, but the need to do so will reduce as the water softens. Once the water has softened, it is advisable to perform future water changes with reverse osmosis water (see next paragraph).
This is a relatively slow method of lowering the hardness of the water in a tank, and one that some people may find a bit tricky, with continual refilling of the softening pillow.
Second, reverse osmosis water can be used instead of tap water for regular small water changes in your tank. Here the tap water passes through a semi-permeable membrane that retains approximately 95% of its mineral content. The water that is produced is very pure and will need to be buffered with essential trace salts and minerals to support your chosen fish, although these will not harden the water again.
After a series of small regular water changes with reverse osmosis water in an existing tank containing hard water, you will be able to measure the overall hardness of your water and see that the hardness is decreasing. If you are setting up a new tank and it is filled with reverse osmosis water from the beginning, once you have gone through the aquarium maturation period, it will already be at a softness suitable for most soft water species.
Other points worth mentioning
Avoid using decoration in your tank that leaches minerals and makes the water hard and more alkaline, eg limestone, barnacles, etc. Make sure the aquarium substrate you use is free of lime. This should be inert and therefore will not affect the chemistry of the water in your tank.
Soft water systems are often quite acidic. Some aquarists use bog wood in their tanks as decoration. This tends to leach out the tannins in the water, which actually helps make the water softer and more acidic. The downside is that the tannin will discolor the water (although some aquarists don’t find this unpleasant), but this can be easily removed by adding some activated carbon to the filter if desired.
A slightly more acidic tank will have the advantage of controlling any fungal infections more naturally, and soft water tanks will generally have far fewer snails as there is not enough calcium for their shells to extract from the water.
Soft/Acid Water Loving Fish
You should always try to mimic the natural living conditions of the fish you have decided you would like to keep, for long-term good health and vitality. If they are from softer waters, keep them in softer water. The fish will be much happier, they will be much less stressed (and therefore less at risk of certain diseases), they will be more colorful and they will live a much longer life.
You are also more likely to be able to breed certain species in softer waters. The following are some examples of fish that prefer soft/acidic water conditions:
- Most South American Cichlids, eg, Microgeophagus Ramirezi (Ramirezi Fish) , Discus , Angelfish, Apistogramma sp.
- Most loaches (‘Botia’ sp.), eg Clown Loach, Botia dario, Botia striata, Botia almorhae, Botia histrionica, Botia kubotai, Yasuhikotakia sidthimunki, etc.
- Small South American Tetras, for example, Rummynose Tetra, Cardinal Tetra, Emperor Tetra, etc.
- Most Corydoras sp. catfish.
- Most of the beautiful plecos (Loricariidae), eg Golden Nugget, Queen Arabesque, King Tiger, etc.