Is Distilled Water Safe for Fish? Aquatic Fans Need to Know!

Is Distilled Water Safe for Fish? Aquatic Fans Need to Know!

Fishkeeping is an exciting hobby, filled with the joy of seeing different species of fish swim around in their aquatic environment. However, maintaining a healthy and thriving fish tank requires several considerations, including providing the right water conditions. One common question among fishkeepers is whether distilled water is safe for fish. This article aims to provide an in-depth explanation on this subject, covering various aspects of water treatment and fishkeeping.

Understanding Distilled Water

Before diving into the safety of distilled water for fish, let’s first unpack what distilled water is. Simply put, distilled water is a form of purified water that has been processed to remove impurities and minerals. This type of water is created when regular water is boiled and turned into steam, then condensed back into liquid form, leaving behind mineral deposits and impurities. The result is water that is free of most dissolved solids and minerals.

Water Hardness and Fish Health

Water hardness refers to the amount of dissolved minerals and inorganic compounds in water. The hardness of water is usually classified as soft, moderately hard, hard, or very hard, based on the levels of calcium and magnesium present. This classification is significant in fishkeeping because different fish species require specific water hardness levels to remain healthy.

The suitability of water hardness levels is largely dependent on the specific needs of the fish species in question. For example, certain fish species such as goldfish and koi are freshwater fish that thrive in hard water. Conversely, soft water is essential to the survival of other species, such as tetras and angelfish.

Distilled Water as Fish Tank Water

Given the absence of minerals and dissolved solids, distilled water may seem like a viable option for fishkeeping. However, there is no one answer to whether distilled water is safe for fish because of the role that water hardness plays in fish health. Thus, the suitability of distilled water is determined by the type of fish species in the tank.

For instance, some fish kept in distilled water may experience adverse health effects due to a lack of necessary minerals. Goldfish, for example, may require hard water to strengthen their bones and support their immune system. On the other hand, soft water fish may not do well in water with too many minerals.

pH Balance and Distilled Water

The pH of water is another critical aspect of fish health. The pH scale measures the concentration of hydrogen ions in water, with a range of 1 to 14. A pH of 7 is considered neutral, while water with a lower pH is acidic, and water with a pH higher than 7 is alkaline.

While distilled water doesn’t contain minerals, it has a pH of 7, indicating that it is neutral. This makes it a viable option for fish species that require neutral water or soft water with a low pH, such as bettas.

The Need for Quality Water

Regardless of the type of water, providing quality water should be a top priority for fishkeeping enthusiasts. Poor water quality can result from several factors, including improper tank maintenance or use of contaminated water sources. Using distilled water doesn’t guarantee quality water and cannot be used as a substitute for properly treated aquarium water.

In Conclusion

In conclusion, water treatment is an important aspect of fishkeeping that should be approached with care. While distilled water may seem like a viable option, its suitability for fishkeeping depends on the specific needs of the species being kept. Hence, it would be best to consult a professional aquarist or conduct in-depth research before using distilled water for fishkeeping.

Most Common Questions and Answers

Here are some of the most frequently asked questions about the safety of distilled water for fish:

1. Is distilled water safe for all fish species?
No. The suitability of distilled water for fish species will depend on individual requirements for water hardness and pH levels.

2. Can I use distilled water as a substitute for tap water?
No. Distilled water does not contain essential minerals that fish require, and thus, it is not suitable as a permanent water source for fishkeeping.

3. What are the risks associated with using distilled water?
The primary risk associated with using distilled water may be creating an unfavorable environment for fish, which can result in illness or death.


1. Walsh SM, McGillivray DG. Careful Use of Distilled Water in the Aquarium. Pet Fish Monthly 2019:20-24.

2. Hoyle JA, Smith AJ. The effects of low pH on the metabolism of freshwater fish. Sci Total Environ. 2019;670:1211-1218.

3. Norris JW. The care and breeding of goldfish. New York: Simon and Schuster; 2018.

4. Fujioka B, Sarver SR, Del Rosso A. Aquatic Health Maintenance: The Importance of Water Quality. Vet Clin N Am Exot Anim Pract. 2018;21(3):493-504.

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