Tapwater is tapwater, right? I mean, surely it must be the same one day to the next? Unfortunately, there are numerous reasons for variations in tapwater parameters and the cunning aquarist must be able to not only detect these changes but also react to them to ensure stable water for their fish.
Does tapwater really vary?
Despite the fact that there are many guidelines for tapwater safety, these do not extend to complete uniformity from one day to the next and there are variations in tapwater that can have an effect on our fish. PH, hardness and levels of various contaminants all vary and it’s up the the aquarist to keep on top of these.
How is tapwater water treated?
Whilst this may vary from one supplier to the next, the essence of water treatment is to prepare it for safe human consumption (nothing at all to do with keeping aquatic species happy). There are a number of processes involved but a typical water treatment procedure could be as follows:
1. Removal of large particles
Large particles are removed from the water. These could be man-made objects or just leaves and twigs, maybe the odd dead insect or two.
2. Flocculent and removal of small solids
This process involves adding a chemical to the water that causes small particles to stick together so that they become easier to remove. These particles can either be left to sink or made to float so that they can be removed from the water.
The water must now pass through a final filtration stage which will not only remove any of the floc sediment that slipped through the last stage, but will also remove organic compounds using a carbon filter – something many fishkeepers will be familiar with.
Once the water has been filtered, it is disinfected with chlorine which kills germs and bacteria. This ensures that the water that reaches us is safe to drink. It also prevents bacteria that enters the water after it leaves the treatment facility doesn’t pose a health risk once it reaches our taps.
Further chemicals can be added to tapwater for a variety of reasons pertaining to human health. Fluoride, for instance, is added to help prevent tooth decay.
What causes variations?
There are numerous variables that affect how tapwater reaches us. You must remember that there isn’t a single tapwater spring in every region that provides water for the whole county but rather many reservoirs and boreholes from which a water company can supply its customers. In times of prolonged drought or rainfall, your water company may opt to switch supply in order to manage water resources. This can result in changes in water parameters: water from a reservoir will differ to water taken from a borehole that’s already been naturally filtered through rock.
Water pollution – nitrate
Water can still become polluted, notably by fertilisers carried into water sources by rain and surface run-off. Nitrate must fall below 50 mg/l according to the EU standard.
Whilst 50 mg/l is the limit, there have still be instances where nitrate levels have exceeded this. In fact, the environment agency has devised a nitrate vulnerable zones map indicating areas where nitrate pollution might be an issue. Water companies are able to remove nitrate from their water using ion exchange but nitrate levels may vary in accordance with the season and the use of fertilisers.
Test kits and water conditioners
It is very important to test water before you add it to your tank. It is vital that water parameters remain steady and that any changes are carried out as gradually as possible. It is worth noting that some test kits are difficult to use accurately and others are just plain inaccurate. The commonly used API nitrate test kit can give an accurate reading, but the reagent solution needs to be very well shaken before use.
Water conditioners must also be used cautiously as some of the cheaper ones that only remove chlorine, can actually split chloramine into ammonia and chlorine – a deadly combination for any fish! It’s very easy to pick up the very cheapest water conditioner on sale, without reading the small print to ensure it can remove chlorine, chloramine and other water contaminants; not all water conditioners are born equal.
What to do if your tapwater is unsafe for fish
This obviously assumes that you are regularly performing water changes and testing your tapwater. By doing so, you may notice fluctuations in your water parameters, some of which could drastically alter the water in your tank, others meaning the water contains too many pollutants for it to be considered safe for aquatic life.
There are many ways to get around this problem: You could purchase an RO water unit which would give you very accurate control over your water parameters. Alternatively, if it was an emergency and you didn’t have an RO unit, you could take a trip to your local aquatic store (as if you needed an excuse) and purchase some of their own RO water which is generally reasonably priced. Minor changes can be made using DIY methods such as peat filtering, or adding crushed coral to alter the hardness, although high levels of nitrate can be much harder to remove.