Things to Keep Your Fish Alive Over the Winter in 2025

First thing you should have in your pond – a thermometer. Why do we put a floating pond thermometer in? Well, you want to stop feeding the fish once the water temperature drops below 50 degrees, but water temperature and air temperature are two very different things.

It can be coming up here in the next few weeks. We could be in the 40s, but the water temperature is still significantly warmer than that. It’ll take time for that to cool down. It’s not something that adjusts evenly with the air, which is good because you wouldn’t want abrupt changes in the water.

But by putting that floating thermometer in there, you can pull it out, check the temperature. Once we’re down to 50 degrees, you really want to stop feeding the fish. And the reason is because they have bacteria and enzymes and stuff in their intestinal tract, and it becomes dormant when we go below 50 degrees. So the fish can’t process that food out anymore. It’s still fine to feed them right now, water temperatures are still warmer than that. But as we cool down here, it’s kind of like the indicator of when you should stop feeding.

A lot of my customers have a hard time with the fact that you stop feeding the fish. It’s very important you’re not helping the fish because if the digestive track shuts down and you’re still feeding them, they’re going to come to the surface because that’s what they’ve been doing all year. A lot of times they’re instinctive animals. They’re going to eat, but then they can’t process it, and so it creates a bloat and basically like a gut rot, and we don’t want that.

Most ponds have algae or some type of stuff inside the pond. There’s natural food for them there. It’s kind of like us eating a salad. It’s very easy for them to digest that type of food, but when you put fish food pellets in that are high in protein, it’s kind of like us trying to digest just a steak. It’s definitely way more difficult for the fish to digest that high protein, and they really don’t need it as they’re starting to go dormant. They’re going to go to the bottom, they’re not going to move around much, so they’re not consuming a lot of energy.

The other thing is nets. And nets are super, super important. This time of year, the leaf drop is going to start happening here. Some of it has already stressed and dropped a lot of leaves.

By putting that leaf net on there, it will help prevent debris from ever getting in the water column. And then you can just take a little leaf blower and blow air onto the net, and it will lift the leaves off the net and blow it out into the yard. It just makes maintenance easier on it. 

And as the plants start to die, like your lilies and irises and things like that, and we cut those back, now they’re exposed to predator birds. And so by putting the netting on as the foliage comes off the pond, you’re protecting the fish as well. So it’s kind of like a win-win.

The other thing you want in your pond is an airstone. We use aerators in the fall when we shut our pumps off and filters off. This time of year, you want to put some type of aeration in the pond. The aerators are less expensive than the heaters to buy and also significantly less expensive to operate. You’re looking at a quarter a month in power use or $60 a month in power use. Significant difference. And it’s better for the environment and the fish to have the aerator than just the heater by itself.

There’s a single-stone kit, a two-stone kit. So you match the aerator really to your pond size. And if people have a heater, I still recommend they put the heater in the pond. They can put the heater above the aerator. Most heaters, good heaters, have a thermostat in them, and they’ll only turn on when they need to.

The airstone is bringing warm water to the surface with the air bubbles, and so it keeps the heater from turning on unless we drop into, you know, teens or single digits, and then the heater will activate.

A lot of people misunderstand what a heater does. It does not heat the entire pond. It keeps an opening in the ice. It prevents the pond from freezing solid, and when you freeze solid, you block the ability for oxygen to get into the water. And so the fish, as they consume oxygen by breathing, you don’t want that oxygen level to drop too low. That’s why running an aerator is such a better option than a heater, not just for the financial reasons but for the benefit of the health of the fish.

We have power outages in the winter, you know, ice storms. You know, vehicles hit a pole and knock the power down. If you’re just running a heater, that heater, that small opening the heater creates can freeze over, and then the fish are consuming oxygen and the level starts to drop.

If you were running an aerator, you forced large amounts of oxygen in the water, and so you have a much longer period of time before it becomes a critical level. And the aerator is just a really good way to keep the fish happy and healthy, and some people run them year-round. You can even run them in the wintertime or summertime. You can put the stone at the bottom in the summertime. In the winter, we recommend the stone only be down about a foot because we want to leave some of the pond water at the bottom. 

It’s where the fish are going to go. It’s where the water is the warmest. Mother Nature geothermally is keeping that water warm. We do not want to pump 10-degree air down there. So we’re going to go down about a foot with the air stone in the wintertime, and that changed back in 2010 because we always recommended stones on the bottom. 

But in 2010, we had one of our coldest winters in Ohio’s history. It was like 28 days where we were under 20. So the plants had a hard time that year, but also a lot of the ponds that had never had a problem putting the air stone at the bottom all of a sudden started having fish kills. And it was because we were pumping negative 20-degree air down into 50-degree water, and we super-cooled the whole pond. So that’s why we recommend the air stone only a foot deep.

That leaves some of the water on the very bottom warm, and as the air is pumped into the air stone, it creates a current in the pond. So even though the air stone is not at the bottom, that water is also getting oxygenated because it creates a current that spirals around.

Questions? Email us at [email protected] or call one of our two locations: Portage (330-499-0101) or Everhard (330-492-1243).