Here's why:
* Predation: Goldfish, even parents, will often eat their own eggs. This is a natural instinct, and it's difficult to train them out of it.
* Stress: The parents might accidentally harm or injure the eggs while navigating the tank or trying to eat them.
* Water quality: The parents' waste can pollute the water and harm the developing eggs.
How to separate them:
* Separate tank: The ideal solution is to move the eggs to a separate tank, ideally a breeding tank with a fine-mesh bottom to prevent the fry from falling through.
* Breeding box: You can also use a breeding box, which is a small, mesh container placed within the main tank. This allows the eggs to be kept separate while still being in the same water environment.
Important Note: If you are planning to breed goldfish, it's crucial to research the specific species and their breeding requirements. Not all goldfish species are good breeders, and some may require special conditions.