Here's why:
* Goldfish grow: They can get much larger than their initial size, especially if well cared for.
* Waste production: Even small goldfish produce a surprising amount of waste, which requires ample water volume to keep the tank clean.
* Space to swim: Goldfish need room to swim around, even if they're not fast swimmers.
Important Note: The 10-gallon minimum is for a single goldfish. For every additional goldfish, you should increase the tank size by at least 5 gallons.
Always aim for a larger tank if possible. A happy and healthy goldfish is a joy to watch!