The common middle-level ornamental fish are fairy fish, colorful fairy fish, goldfish, brocade carp, map fish, parrot fish, traffic light fish, red-nosed scissors fish, lotus lantern fish, penguin fish, etc. These are common ornamental fish, and they all like to move in the middle of the fish tank. Besides ornamental fish, some food fish are also middle-level fish. For example, common silver carp, bighead carp, grass carp and herring are all middle-level fish. Although they are all called middle fish, it doesn't mean that they don't move in the upper and lower layers, but the area where they move is often in the middle layer.

There are also many ornamental fish that like to move in the upper layer, such as arowana, guppy, Mary fish, water-shooting fish, red swordfish and zebrafish. They like to move in the upper layer of fish tanks, and most of them have the habit of jumping tanks. When raising the upper fish, the breeder needs to add a cover to avoid injury after jumping into the tank. If the lid cannot be added, the water level can be lowered to avoid jumping the cylinder.

The lower fish are mainly fish living at the bottom of the water or fish tank, such as rays, scavengers, smooth sailing fish, rat fish, carp, crucian carp, loach and so on. These fish prefer to move underwater, and their biggest feature is that their upper jaw is longer and their lower jaw is shorter, which is also their long-term evolution and evolution.