Fish that don't sleep at night?
For starters, fish don't sleep in general. Fish go into a resting period and usually that has to do with the place the sun is in or if it is a fish in a tank, whether the lights are off or on.
Secondly, some fish move all day and night to keep away from predators and to insure water is passing over there gills. A fish will move while resting, when they do they are moving slowly and lower in the tank. If you have a few small fish they will follow each other and wake each other up. (Hardy fish are the best ones).
Lastly, fish are great pets for people who are half commited pet owners!
Treat them well
Summary: Fish do rest but their "sleep" is different than land animals. Although most fish "sleep", some are still under speculation because some animals need to move to survive, similarly to a shark. Most all fish spend time in an energy-saving state that can be called "rest", and we might even call their behavior "sleep", though it is probably different than "sleep" in most land animals. Many fish, like Bass and perch, rest on or under logs at night. Coral reef fish active in the day, hide and rest in crevices and cracks in the reef to avoid being eaten at night. The resting behavior of fish is very different from their behavior the rest of the day. Many minnows, for example, which are very active in schools during the day, scatter and remain motionless in shallow water at night. Many fish "rest" or "sleep" during the day and are active at night instead, but almost all fish sleep.