Can I Use Distilled Drinking Water in My Fish Tank?

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Water should be tested to make sure it does not contain substances that are toxic to fish.

Distilled water has been processed to remove all impurities. However, since this process also removes minerals from the water, you should not use it as water for the fish tank. You can use a small amount to top off your tank or treat the distilled water to make it usable if necessary.


What is distilled water?

Distilled water is produced by boiling water and capturing the steam that rises. This process is very effective at removing impurities. Distilled water is very affordable to purchase.


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Unfortunately, this includes removing minerals from the water, including calcium, sodium, and magnesium. Both fish and aquarium plant life need these minerals to live. In addition, the minerals are critical to maintaining a consistent pH level in the water. If the pH fluctuates too much or is outside the recommended range for your fish, it can be fatal.


Distilled water for a fish tank

Can you use distilled water in a fish aquarium? On its own, pure distilled water is not suitable for fish tanks. If you need to add a small amount of water to your tank, you can do so with some distilled water that you may have on hand. However, you can treat the distilled water to make it safe for your aquarium.


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To do this, simply add minerals back into the water. Remineralizers are available for purchase. Follow the package instructions to determine how much of the product to add. If you have a saltwater aquarium, check the label on the salt mix. In most cases, this mixture includes the necessary minerals.


Aquarium water requirements

Before adding fish or plant life to the treated distilled water, be sure to check the water chemistry. Start by checking the water pH with a pH test strip. The recommended pH range can vary depending on the type of fish you keep, but for most freshwater aquariums, a pH between 6.5 and 8.0 is suitable.


KH is a measure of the number of carbonates in the water and is measured in degrees of KH (dKH) or parts per million (ppm). For most fish, aim for 4 to 8 dKH or 70 to 140 ppm. Correct KH levels ensure the water pH levels remain at appropriate levels.


GH, or general hardness, measures the amount of calcium and magnesium in the water. It is measured in ppm or degrees of GH (dGH). The amount of minerals needed varies by species, but in most cases, 4 to 8 dGH or 70 to 140 ppm is acceptable. Distilled water can help to reduce water hardness if necessary.


Fish tank water changes

Treating distilled water is not only necessary for filling a new aquarium but it is also required when using distilled water for water changes. Regularly cleaning your fish tank is important to keep it clean and to keep nitrate levels from reaching toxic levels.


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The frequency of water changes depends on several factors, such as the strength and quality of your filters and the number of fish in the aquarium. Larger filters can help keep the water cleaner. Fish waste and excess food can all dirty the water, so take care not to overfeed your fish.

Change up to 30 percent of the water volume when you clean the tank. Avoid changing too much water, as this can stress your fish.



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