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What do you really mean when you say fish are “dormant” for the winter? Do they sleep? | Decorative Ponds & Water Gardens Q & A

Q: What do you really mean when you say fish are “dormant” for the winter? Do they sleep?

Q: What do you really mean when you say fish are “dormant” for the winter? Do they sleep?

Diane – Wells, ME

A: When the days shorten and temperatures drop, koi and other pond fish enter into what’s called torpor, or a period of decreased physiological activity that allows them to save energy. They don’t sleep the winter away, but they do essentially hibernate—their metabolism slows, they require less food, their activity level drops and their body temperatures reduce.

How do they know they need to hibernate, and what can hobbyists do to make their finned friends’ winter torpor restful? Read on to learn more.

Mother Nature’s in Charge
Fish don’t use calendars to decide when to take their winter snooze. Instead, they follow Mother Nature’s lead. Because fish are cold-blooded, their metabolism reacts to the external environment. When the water temperature falls, so does their activity level: Their appetite dwindles, they digest food more slowly, and they expend less energy. In the spring when temperatures warm back up, the fish will naturally come out of their torpor. They’ll start to seek out food as their metabolism increases, and they’ll become active once again.

Suspended Animation
You’ll know when your fish go dormant. They won’t lie down on the pond’s bottom or curl up in their cozy Koi Kastle, but they will float upright, tuck in their fins and remain suspended in the water. As the fish hover there, you may still see some super slow movement, and they may also wind up facing in the same direction as if they were heading somewhere at less than a snail’s speed.

Sweet Dreams, Koi!
Here are four ways to give your koi a peaceful winter rest:

  1. Set up an aeration system to keep the water pumped full of oxygen. Even though they’re hibernating, your fish will still need some fresh O2.
  2. Install a de-icer to keep a hole open in the ice and allow for gas exchange. If the pond freezes over, use warm water to reopen a hole; do not bang on the ice to crack it, as doing so can stress your fish.
  3. Keep as much debris out of the pond as possible to prevent muck buildup over the winter.
  4. Let the fish be. Don’t try to get them to move or swim or wake up from their slumber. Keep an eye on them, but leave them alone until they wake up on their own.

Pond Talk: Have your fish started hibernating yet?

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How do fish go dormant? Are they really asleep? – Decorative Water Gardens Q & A

How do fish go dormant? Are they really asleep?

How do fish go dormant? Are they
really asleep?

Ryan – Falston, MD

With the warm days of summer now a distant memory and fall following in its footsteps your Koi are left with a few months of cold weather with nothing to do but relax. Since they don’t have miniature submerged Koi calendars to check what is it that tells your fish it is time to hibernate?

Koi are cold blooded creatures which means their body temperatures and activity levels are directly correlated with the ambient temperature. Koi are active and alert when their environment is warm and will start to slow down as the water temperature decreases. Once the water temperatures start to dip below 46°F your fish tend to stop eating and will retreat to the bottom of the pond. Your fish use the decrease in temperature along with the shortening day lengths as a trigger to prepare for winter. As the water begins to cool your fish will become less active as their bodily functions slow down. Less activity means a slower digestive process, less demand for food. It is this decrease in food digestion that warrants the use of wheat germ based foods like Pond Logic® Spring & Fall Fish Food. These types of food are easier to digest that regular food reducing the risk of leaving undigested food to rot inside a dormant fish which can potentially be fatal.

As the temperatures continue to decline towards 40°F, the blood flow and respiratory rate of the fish will drop to an extremely low rate where their body is hardly functioning. You may hear people say that your Koi are sleeping in the winter and while fish do sleep this goes way beyond the standard drop in bodily functions associated with some much needed shut-eye. This extreme internal slow down ensure survival with even the most limited resources with cases of dormant fish lasting 150 days without food.

The whole over-wintering scenario sounds a little extreme to us but it is truly a natural and normal process for your fish. They do not require much attention in the winter but there are a few things you can do to ensure their winter break is a success. When a layer of ice begins to form over the pond, maintain an opening for gas exchange using your aerator or a de-icer. Also, make sure you feed with a cold weather formulated fish food as water temperatures approach 50° so your fish are able to safely digest it before hibernation begins. You can use a pond thermometer to keep track of the water temperature in your water garden.

Pond Talk: What do you do to help your fish through the winter season?

Get your fish ready for wither with Pond Logic® Spring and Fall Fish Food!