Goldfish is a very common ornamental fish, which has a long culture history in China. It has many varieties and different personalities. It is usually divided into four species, namely grass species, culture species, dragon species and egg species. No matter what kind of goldfish, the consumption of oxygen is not high, so it is perfect to raise it in a fish tank without oxygen.

Betta is a combative fish known by its name. This kind of fish can't be mixed. Two male betta will fight together, so it can only be raised alone. However, as a fish of the family Percidae, one of its major characteristics is the suprambranchial organ, which can make it swim to the water surface to breathe in an environment with low dissolved oxygen, so it can also be raised in a fish tank with low oxygen.

Guppy is a common small tropical fish. Its length is only 3-4 cm, and its demand for oxygen is not high, so it can be fed in a fish tank without oxygen. The tail of this kind of fish is very big and beautiful. When it is raised artificially, it is necessary to prevent diseases such as needle tail, otherwise it will greatly reduce its ornamental value.

Lamp fish refers to the fish of Lamp family, which are produced all over the world, but they are all small ornamental fish and very beautiful. Because of its small size, the demand for oxygen is very small, and it can be fed without oxygen. It is worth mentioning that this kind of fish is very suitable for raising in grass tanks, which is a very good ornament.

Zebrafish has stripes on its body surface and looks similar to zebras, hence its name. This kind of fish does not require high water quality, and swims almost all day long. It is also a very good ornamental fish. Because of its small size, it can be raised without oxygen.