Goldfish itself is a kind of high-oxygen fish. A centimeter of goldfish needs 1 liter of water. A goldfish needs at least 60 square centimeters of oxygen surface to be oxygenated, but it must have a filtering device. Goldfish are relatively cold-resistant, and as long as they don't suddenly cool down, there is generally no danger to their lives.

Excellent varieties of grass goldfish (crucian carp), gold, dzi beads and lion's head.

As long as the water quality is well controlled, it will be easier to maintain.

Personally, I don't recommend koi fish unless your fish tank is very big. This kind of fish grows fast and the aquarium will soon become crowded.