How to Make a Hole in Pond Ice

Pond DeicerYour fish friends are semi-dormant during the winter, but they still need to breathe. That means you need to make sure the carbon dioxide they exhale has a way to exit your pond. An iced-over pond traps in these bad gases, so, when the mercury drops, you need to either make a hole in the ice or prevent your pond from freezing over in the first place.

You can't just smack at the ice with any old blunt object you have lying around, however. Keep reading to learn how to safely make a hole and keep you fish happy all winter long.


At a Glance: How to Make a Hole in Pond Ice

  • Use a deicer.
  • Place a pot of hot water on top of the ice.
  • Use a rough-toothed saw.
  • Avoid hitting the ice or doing anything else that would send strong vibrations through the pond.

An Escape Hatch for Bad Gases

Before we talk about how to make a hole in your pond's ice, let's talk about why it's so important to do.

Your koi and goldfish enter a semi-dormant state called torpor in the winter. They don't eat or move much while in this almost-hibernation, but they continue breathing in oxygen and breathing out carbon dioxide, just like they would in warmer weather.

Now imagine you had to live in a box the size of your pond. You, like your fish, need to breathe in oxygen and get rid of the carbon dioxide you're breathing out. You would absolutely want a hole in the top of that box. That's how your fish feel when the pond freezes over.

Suffocation is one of the leading causes of winter fish death. You don't usually need to panic if your pond freezes over for a couple days before you get a chance to make a hole in the ice, but you'll want to make sure you fix the problem as quickly as possible.

Mind the Lateral Line

Fish Lateral LineWhat’s the best way to make a hole in your ice? Here’s what we DO NOT recommend: blunt force trauma via axe, sledge hammer, baseball bat, 2-by-4, large rock or garden gnome.

Pounding on the ice sends strong vibrations and shockwaves through the water that can damage a system of organs in your fish called the lateral line. The lateral line - which you might be able to see if you look closely at the side of your koi - acts as your finned friends' central navigation system, helping them sense movement, vibration, depth, water pressure and orientation. The lateral line also helps schooling fish sense what their buddies are up to.

So how does this system work, and why is blunt force to the top of your pond ice so bad for it? Essentially, water enters holes in the scales that line your fish's side, disturbing an underlying layer of mucus. The mucus vibrates in response to any changes caused by the water, and these vibrations tell your fish's central nervous system what to do. Hitting your pond ice creates vibrations way stronger than this complex system can handle - causing permanent damage to or even killing your fish.

So before you reach for your shovel or hammer, here are a few better ways to open a hole in the ice:

  1. Place a pot of hot water on the ice and watch it slowly melt through. You may need to do this a couple times depending on the thickness of the ice.
  2. Use a deicer. Our 300 Watt deicers typically melt through about 1 inch of ice per hour. (Your ice might end up 2 to 6 inches thick in extreme cold.)
  3. Use a rough-toothed saw to cut a hole.

An Ounce of Prevention ...

Dealing with an iced-over pond is no fun. Nobody wants to hang out in the cold waiting for ice to melt when they could instead enjoy looking out the window at a beautiful pond from the comfort of a warm living room.

Luckily you can take a few steps to prevent your pond from freezing over in the first place. The easiest method is to keep your pond running year-round. The flow of a waterfall might keep just enough of a hole open to let those bad gases escape your pond and keep oxygen circulating to the fish huddled under the ice.

Keeping your pond running in the winter does, however, have some disadvantages, especially if you plan on being away from your house for any extended period of time. You'll have to keep a close eye on the pond, especially in extreme cold, to make sure the waterfall is keeping that hole open. If your pond does manage to freeze over while it's running, you risk not only suffocating your fish but also having water from the waterfall flow over the top of the ice and out of your pond. You also need to keep an ear out for the sounds of a laboring pump in the winter. If it sounds like it's working harder than it should be, you'll need to shut it down.

The easiest way to keep your pond from freezing over in cold temperatures is to unplug the pump, drain your pond plumbing and install an aerator and a deicer. The aerator will ensure your fish have plenty of oxygen circulating through their water, while the deicer will keep just enough of a hole open in the ice to let out the bad gases. The deicer will not warm the overall temperature of your pond water, meaning your fish will still go into their winter torpor the way nature intended. You deicer also shuts off when the water warms up, so you never have to worry about it wasting electricity.

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