Here's why:
* Comet goldfish get large: They can grow to be 12 inches long. A 5-gallon tank is far too small for even a single comet.
* Goldfish produce a lot of waste: This can quickly pollute a small tank.
* Goldfish need space to swim: They are active fish that need room to move around.
Here's a better rule of thumb:
* For a single comet goldfish, you need at least a 20-gallon tank.
* For multiple comets, you'll need even more space.
Always prioritize the health and well-being of your fish. Overcrowding and inadequate tank size can lead to stress, disease, and shortened lifespan.