It's a common question about fish in general and koi in particular. Do Koi sleep? The answer is both yes and no! In humans, sleep is essential and enables the body and mind to recharge. Of course, human sleep involves relaxing until we fall into an unconscious state with our eyes closed and there are several stages of sleep for us including dreaming.
Periods of Rest
Koi do not sleep in the same way as humans. Theyare unable to close their eyes because they do not have eyelids and, as far as it is possible to tell, neither do they dream. Koi do require rest of course but these are a case of periods of deep rest rather than sleep as we are familiar with.
Koi engage in rejuvenating periods of rest. When they are resting, koi will float in one spot in the pond for an extended period of time. They will usually choose a location in the middle of the pond or towards the bottom as this is where they will feel most safe from predators. Koi may appear not to be moving at all but will, on closer inspection, be making subtle movements to maintain their position in the water.
Koi usually choose to rest at night but if bugs are active after dark, the fish may take advantage of the opportunity to feed and then engage in some rest during the day. The fish will normally group together and sleep at the same time.
Cold weather influences activity levels in koi carp. As the water cools their metabolisms slow down and they stop feeding. In extremely cold conditions the fish will enter a state of semi-hibernation and may retreat to the bottom of the pond to keep away from potential predators.
Whilst resting is entirely normal behaviour for koi, a listless fish could be exhibiting signs of illness. It is important to familiarise yourself with your koi's usual behaviour so you can more easily recognise any potential issues shouldthey arise. Koi may become listless or lifeless and lie on their sides. This is often put down to sleeping sickness, which is a generic condition thatcan be indicative of a variety of infections. If you are in any doubt about the health of your koi carp, seek out the help of an expert in such matters. So there you have it, do koi fish sleep? The answer is both yes and no!