Fish sleep. Although it lives in the water, it can still rest. Normally they swim in the water, but when they are suspended in a certain position for a long time, they are sleeping. Different fish have different habits when they sleep, some will hide in the water and grass, others will bury themselves in the sand.
1. Hiding in the dark: Many common fish sleep in the dark, such as goldfish, carp, crucian carp and so on. Some of them will hide in the middle of water and grass, some will be in the crevices of stones, so as to avoid the attack of other enemy creatures and ensure their own safety.
2. Hide in the sand: For some fish, the living area is a sandy bottom, without water plants and stones for them to hide, but they can bury themselves in the sand to sleep. For example, Leptura gracilis, Broccoli and Haplostethus, etc., are all like this when they sleep.
3. Secrete bubbles: There are some special fish that can secrete a gelatinous substance before going to bed and wrap themselves in it. This substance will harden when exposed to water and will flow out of a hole to facilitate its breathing. The fish with this characteristic are mainly crackhead and Nanyang parrotfish.
4. Sleeping while swimming: There are some special fish in the ocean. Their metabolism is relatively fast, so they have to swim all the time, even when they are sleeping. For example, sharks, tuna and so on are all like this, so they will sleep while swimming.
