* Lack of Minerals: Purified water removes almost all minerals, which are crucial for goldfish health. Minerals like calcium and magnesium help with bone development, gill function, and overall well-being.
* pH Imbalance: The lack of minerals can cause a drastic change in the water's pH, making it too acidic for goldfish. This can lead to stress and health problems.
* Osmotic Stress: Goldfish have a delicate balance of electrolytes in their bodies. Using purified water can disrupt this balance, causing them to lose water and electrolytes, which can be fatal.
Instead of purified water, you should use:
* Dechlorinated Tap Water: Most tap water contains chlorine, which is harmful to fish. Use a water conditioner to remove chlorine and other harmful chemicals before adding it to the tank.
* Aged Tap Water: Allow tap water to sit in an open container for 24 hours before adding it to the tank. This allows chlorine to dissipate naturally.
* Bottled Spring Water: Make sure the bottled water is specifically designed for drinking and doesn't contain added minerals or chemicals.
Always test the water parameters (pH, ammonia, nitrite, nitrate) regularly to ensure the water is safe for your goldfish.
It's best to consult with a veterinarian or experienced fish keeper if you have any concerns about your goldfish's water quality.