Your aquatic or pet shop will be able to provide you with expert advice on what proportion of water change is suitable for your tank or pond as many fish are sensitive to their environment.
Before you add tap water to your fish tank or pond, there are a few steps to take. This is because:
The temperature and acidity of tap water is likely to be different to the water in your tank or pond
Traces of metals are harmless to us but can be harmful to fish
The small amount of chlorine can be harmful to fish
Getting the water to the correct temperature
Tap water is usually much colder than the temperature of the water in your aquarium or pond. Even if the difference doesn’t feel that much to you, fish are much more sensitive to differences in temperature. This is because they are ectothermic – their body temperature is maintained by the water they live in.
What to do
Run the water from the tap and then leave it to stand. Wait until the water reaches a similar temperature to the water that is already in your tank or pond before you add it.
Reducing traces of metals in the water
Water that has been standing in your plumbing and pipework can absorb tiny amounts of metals such as copper and zinc used in domestic plumbing fittings.
This is harmless to us, but can be harmful to your fish.
What to do
Use water from the cold tap that’s nearest to where your water supply enters your house (this is normally your kitchen tap). Allow the tap to run for a little while first. You can also buy special preparatory products from your local pet shop or aquarium to reduce any metals.
Tap water contains very small amounts of chlorine that we use to remove harmful bacteria. Although chlorine is completely safe for us, it can be very dangerous to fish.
What to do
There are various ways you can remove the chlorine from your water. They include:
• adding a specialist water conditioner to the water before you add it to your aquarium or pond – you can
get this from your aquatic or pet shop
• adding activated carbon granules – you can get these from your aquatic or pet shop
• leaving the water in an uncovered bucket for 24 hours – this will allow the chlorine to evaporate
• using a fine spray when filling up a pond – this will aerate the water and remove the chlorine.
Getting the correct water acidity
Different species of fish require water with different acidity levels. For example, saltwater fish will have very different pH needs to freshwater fish. It’s likely that the acidity of the water required by your fish will be different to the water from your tap.
Sudden changes in acidity can also be very harmful to your fish.
What to do
You can buy a pH test kit from your aquatic or pet shop to test the acidity of your water. If you find that you need to adjust the acidity of the water, you can also buy kits to adjust the acidity of the water.
Depending on the fish that you keep and the acidity of your water, some specialists recommend slowly getting your fish used to the acidity of the water available to you. Your aquatic or pet shop will be able to
advise you on this.
Reducing phosphate levels
Phosphate is a naturally occurring chemical that may be found in your tap water at a level that is too high for your fish. However, the main sources of phosphate in aquariums and ponds are decaying fish food and fish waste.
What to do
Your aquatic or pet shop will be able to give you more information on how to measure and reduce phosphate levels in your aquarium or pond.
Maintaining your aquarium or pond
The other key issues to do with the water quality in your aquarium or pond are to do with good care and maintenance.
Controlling nitrate and associated compounds
Nitrate is a chemical compound that is present in water. Most fish can tolerate much higher levels of nitrate than those allowed in drinking water. Fish food, fish waste and fertilisers added around ponds can increase
the nitrate in the water.
Nitrate itself isn’t a problem to fish, but in certain conditions the nitrate degrades into smaller compounds, such as ammonia and nitrite, which can be harmful to fish.
You can reduce the risk of the nitrate degrading by:
• removing decaying plants
• keeping filters clean
• avoiding over-stocking or over-feeding
• using low-nutrient compost if you have plants in your aquarium or pond
• not using fertiliser in areas around your pond.
If your tank or pond gets too much light, has high nitrate or phosphate levels or not enough plants, algae can start growing.
To control algae growth, you can:
• restrict the light – for example by providing shade, keeping lights on for shorter periods and keeping the
fish out of direct sunlight
• add fast-growing plants that will take up the extra nitrate and phosphates, or introduce species of fish
that graze on the algae.
Getting a water quality report
You can buy test kits to check the concentration of chemicals and compounds in your aquarium or pond. However, these kits may not be appropriate for accurately measuring the low levels of compounds that are found in drinking water.
If you find that you need more detail than a kit can give you, we can provide you with a water quality report for your area