Here's why:
* Comet goldfish grow large: Comet goldfish can reach up to 12 inches in length, and even more in ideal conditions. Two of these fish in a 5-gallon tank would be severely overcrowded.
* Waste production: Goldfish are messy eaters and produce a lot of waste. A small tank can't handle the ammonia levels produced by two goldfish.
* Stress and health issues: Overcrowding leads to stress, which makes goldfish more susceptible to diseases.
Minimum tank size for two comet goldfish: A 20-gallon tank is considered the minimum for two adult comet goldfish.
Remember: The bigger the tank, the better! Goldfish are happiest and healthiest in spacious environments.