Winter Pond Guide
What Size Pond De-Icer Do I Need?
Short answer: a de-icer is not sized by your pond's gallons. It is sized
by how cold your winter gets and how big a hole you need to keep open.
Almost every "what size" chart online gets this wrong, so here is what
the wattage actually buys you.
First, the thing most people get backwards
A pond de-icer does not warm your pond. It has nowhere near
enough power to raise the temperature of a few thousand gallons, and you
would not want it to. Fish overwinter fine in cold water.
Its only job is to hold one opening in the ice. Through the
winter, leaves and waste on the bottom keep decomposing and releasing gas.
Seal the surface completely and that gas has nowhere to go. That is what
kills fish over winter, not the cold.
This is also why wattage maps to climate rather than volume. A 100 watt unit
keeps a modest hole open in a mild winter. The same unit in a Minnesota
January will lose the fight.
Pick your wattage
EasyPro rates the Thermo-Pond line by wattage, not by pond size, so that is
how we list it. The winter column below is our own field guidance as a pond
dealer, not a manufacturer rating. When you are between two, go up.
Worth knowing: the 250 watt TPH250 is currently the cheapest of the four and
carries a two year warranty against the TP100's one year. Unless you
specifically want the lowest running cost, it is the better buy.
The TPH250, TPH750 and TPH1500 also drop the float and work as a bottom
heater. All four carry a 12 foot cord, so plan your outlet distance.
The other way to keep a hole open
A de-icer is not your only option, and plenty of pond keepers run both. An
aerator set shallow keeps water circulating at the surface
and holds an opening without any heating element at all. It also keeps
oxygen up all winter, which a de-icer does not do.
The rule is to keep the diffuser high, not on the bottom. Running air from
the deepest point in winter mixes the warmer bottom layer your fish are
resting in up to the surface, and that genuinely does harm them. Shallow
placement, and you get the hole plus the oxygen.
Aerators, by pond size
These ratings come from the manufacturer and assume a normal fish load. Heavy
koi stocking, size up.
Deeper water: size by airflow and depth
Past about 8 feet, depth matters more than volume, because the compressor has
to push air against the water above it. These are real rated figures.
Three things that kill fish every winter
- Breaking the ice with a hammer. The shockwave travels through the water and can kill fish outright. If the pond has sealed over, set a pot of hot water on the ice and let it melt through.
- Running the waterfall all winter. A waterfall supercools the whole pond and strips the warm layer at the bottom. Most keepers shut the pump down and switch to a de-icer and shallow aeration.
- Sealing the pond completely. Netting and covers keep leaves out, which is good, but you still need one open hole for gas exchange.
Not sure which way to go? Tell us your pond size, depth, and roughly how
cold it gets where you are, and we will tell you what we would run.
We do not upsell wattage you do not need.
Common questions
What size de-icer do I need for a 1,000 gallon pond?
De-icers are not rated by gallons. For a 1,000 gallon pond in a typical northern winter, a 250 watt unit like the TPH250 is the usual choice. In a mild climate a 100 watt TP100 will hold a hole. In sustained sub-zero conditions, step up to 750 watts.
Does a pond de-icer heat the whole pond?
No. It only keeps one opening in the ice so gases from decomposing matter can escape. Heating a pond is neither practical nor necessary. Fish overwinter safely in cold water as long as the surface is not sealed.
Should I run a de-icer or an aerator in winter?
Either keeps a hole open. An aerator also maintains oxygen levels through the winter, which a de-icer does not. Many pond keepers run both. If you use an aerator in winter, place the diffuser shallow rather than on the bottom so you do not mix the warmer bottom layer where fish are resting.
Can I just break the ice instead?
No. Striking the ice sends a shockwave through the water that can kill fish. If your pond has iced over, melt an opening by setting a pot of hot water on the surface. Never hit the ice.
How much does it cost to run a pond de-icer?
It depends on wattage and how often the thermostat calls for power. Thermo-Pond units are thermostatically controlled, so they only draw power when water temperature approaches freezing rather than running constantly. A 100 watt unit costs less to run than a 1500 watt unit, which is the main reason to size down if your winters are mild.
Do I still need pond netting if I have a de-icer?
Yes, and net before the leaves drop rather than after. Leaves that sink and decompose over winter are what produce the gases the de-icer's opening lets out. Less debris going in means less gas to vent and an easier spring cleanout.
