The water may look crystal clear and smell perfectly clean, but it may still contain levels of substances toxic to your fish.
Take a close look at your well water analysis or contact your local water department to request a water analysis. Though the water will vary from day to day, the analysis will enable you to make informed decisions about what you need to do to maintain healthy water conditions in your aquarium.
Most municipalities add chlorine or chloramine to the water. Both are detrimental to the gills of your fish. But did you know that not all dechlorinators available are effective on chloramines? Read the labels. If you have high levels of chloramines, you may want to select a product designed specifically for chloramine control.
Well water can contain phosphates, a popular ingredient in lawn and garden fertilizers. Plus, some municipalities add phosphate to protect their pipes. Although these are not toxic, they can fuel aggressive algae growth in your aquarium.
Whether you have city or well water, potentially harmful heavy metals are likely present.
Iron, for example, is commonly found in tap water and can also come from galvanized pipes in the home. Though not usually found in high enough concentrations to be toxic, it too can energize algae.
Copper can be found in trace amounts in wells, but can also come from copper plumbing. Most fish can tolerate copper in low levels for a short amount of time, but it can be particularly devastating to any aquarium containing invertebrates. Once copper has been introduced in a reef aquarium, extreme measures may be needed to re-create a suitable environment. Even the substrate (gravel) used in a once-contaminated aquarium must be discarded.
Some fish, such as koi, are highly intolerant to copper. They build up copper within their body tissue and may eventually die of heavy metal poisoning. If you choose to keep copper-sensitive fish, invertebrates, or a reef aquarium, a copper test kit is a must have. It is an inexpensive way to help head off serious problems.
Some water conditioners can detoxify heavy metals, allowing them to precipitate so they can be removed by your filtration. But if your test indicates the presence of high levels of copper, you might want to consider purifying the water with the addition of a Reverse Osmosis unit (RO).
If you have copper pipes, it is always a good idea to allow the water to run before using it in your aquarium. This will help rinse out any loose molecules of copper that have built up in the pipes.
Testing your tap water regularly for heavy metals will help you maintain these minerals and their by-products at safe levels.