Why do black goldfish sit at the bottom of tank?

Goldfish, regardless of their color, do not sit at the bottom of the tank for any specific reason related to their coloration. There are various factors that can affect a goldfish's behavior, such as water quality, tank conditions, and health issues. If a goldfish is sitting at the bottom of the tank, it is important to observe its behavior and check the tank environment to identify the root cause and take appropriate measures to ensure its well-being.