It is impossible to raise koi without oxygen, unless it is raised in an outdoor fish pond, so that there is enough water to meet the breathing needs of fish. This kind of fish is a common ornamental fish, which is relatively large in size, but it is not difficult to raise it, because it is related to carp, has strong adaptability to temperature and environment, and is not very picky eaters. However, because it has a big appetite, it is necessary to control its appetite when feeding, so as not to support it.

1. Lamp fish: Lamp fish is a small fish native to Amazon River Basin in South America. It is not only of various kinds, but also of different colors. Interestingly, they also have the characteristics of group swimming, which is very suitable for raising in grass tanks. Because of its small size, the demand for oxygen is not high, so it can be raised without oxygen.

2. Zebrafish: Zebrafish is a common ornamental fish, and because its genes are highly similar to those of human beings, it is also usually used as an experimental fish. This kind of fish has strong adaptability to the environment. As a tropical fish, it can also live in a slightly lower temperature environment and consume less oxygen.

3. Thai Betta: Thai Betta is a kind of betta, which is produced in Southeast Asia and belongs to aggressive fish with strong adaptability. In addition, it belongs to the family Percidae, which has a characteristic, that is, it has the suprambranchial organ, which allows it to swim to the water surface to breathe in the environment with low dissolved oxygen.