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Pond heater vs air pump: which method holds the hole

Updated: 22 October 2026

The fish need a patch of open water. The argument is pond heater vs air pump: a heating element, or a low-watt pump pushing bubbles. A 1,000 W tube with a temperature knob does not belong on the air-pump side of that argument. Peter F. priced the heaters on the [pond heater comparison](/hub/garden-ponds/pond-heater), from £32.92 to £44.57 on 20 October 2026. The pumps below are the other method. They are not rows in that table, and there was no frost test. A qualifying purchase can earn a commission at no extra cost to you.

The fish need a patch of open water. The argument is pond heater vs air pump: a heating element, or a low-watt pump pushing bubbles.

Our top picks

Blagdon Blagdon Affinity Ice Vent, 50 W

Best overall

Blagdon Blagdon Affinity Ice Vent, 50 W
8.6/10about £40.95
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VIHOSE VIHOSE outdoor pond heater, 1,000 W

Rank 2

VIHOSE VIHOSE outdoor pond heater, 1,000 W
8.6/10about £36.00
View offer
VIHOSE VIHOSE outdoor pond heater, 500 W

Best value

VIHOSE VIHOSE outdoor pond heater, 500 W
8.4/10about £32.92
View offer
On this page
  1. 1.Two ways to keep a patch open
  2. 2.What the low-watt pumps claim
  3. 3.Pence per day, if they never switch off
  4. 4.When the heater is the one to buy

Two ways to keep a patch open

A de-icer puts a little heat at the surface so a hole stays open. In this set that is the Blagdon Affinity Ice Vent: 50 W, listed for ponds up to 5,000 litres. Blagdon says the pond does not need to be heated through. An air pump does not heat the water. Bubbles disturb the surface and, on the maker’s account, keep an area ice-free when the pump is a winter oxygenator, not a deep mixer. The RHS names both for fish ponds. Neither replaces depth. OATA still wants about 45–60 cm for goldfish, more for koi. The VIHOSE tubes are a third thing: a knob aimed at a temperature. The vent belongs in this argument. The types are on the buying guide.

What the low-watt pumps claim

Blagdon’s oxygenator manual says a winter air pump keeps an area ice-free if the air stones sit no lower than 30 cm from the bottom. The single-outlet model is 3.2 W, 140 litres of air per hour, 230 V, with no plug. IPX4 is for the pump on the bank. Other models go up to about 8.3 W. Oase’s IceFree 4 Seasons is 5 W, 230 V, a 10 m cable and no heating element. The maker wants at least 80 cm and rates it to about −20°C. A UK shop listed it at £54.99. Those are claims, not a result against our heaters. Keep the stone high. A 30 cm patio pond has no deep layer for a circulator to leave alone.
Blagdon Blagdon Affinity Ice Vent, 50 W

Testsieger

Blagdon Blagdon Affinity Ice Vent, 50 W
8.6/10about £40.95
View offer

Pence per day, if they never switch off

Ofgem’s cap for 1 October to 31 December 2026 is 26.32 pence per kilowatt-hour on a Direct Debit default tariff in England, Scotland and Wales. It is not your tariff and it does not cover Northern Ireland. On that rate a 5 W pump left on all day is about 3 pence, a 50 W vent about 32 pence, and a 1,000 W element that never switches off about £6.32. A thermostat cuts that heater cost only if it switches near freezing. A dial around 24°C does the opposite. One 500 W VIHOSE review said the unit never shut off, near £3 a day on this rate. The vent does not need the 80 cm Oase asks for. A 40 cm liner may have nowhere to site that circulator.

When the heater is the one to buy

Buy the 50 W vent when the pond is too shallow for a stone held 30 cm off the bottom, or when an air pump has already let the hole close. UK reviews of the Blagdon include both an open patch and nights the hole did not hold. GardenSite and Pondkeeper call the pump the cheaper winter hole. That matches a few watts against 50 W. It does not mean bubbles win every frost. Buy a set-point tube only for a temperature in a small tub, not because an air pump failed. A vent and a pump can share a 30 mA RCD if you accept two cables. You do not need both once one patch is holding. An IPX4 pump stays on the bank. Placement is on the how to use page.

Common questions

Will bubbles keep a hole open in a hard UK frost?
They can, and they sometimes do not. Blagdon’s oxygenator manual says a winter air pump keeps an area ice-free when the stones stay up off the bottom. Oase rates the IceFree 4 Seasons to about −20°C, which is Oase’s claim for that 5 W unit. UK reviews of the 50 W vent also include holes that closed. Look at the patch after a severe night.
Where should the air stone sit?
On the Blagdon oxygenator manual, no lower than 30 cm from the bottom, so the deeper water stays still. The pump itself stays on the bank. The IPX4 mark belongs to that pump. Oase’s IceFree unit wants at least 80 cm of depth because it is a circulator with no element. A shallow raised pond does not have that layer.
Is the Oase unit a heater?
No. Oase specifies 5 W, 230 V, a 10 m cable and no heating element. It moves water. A UK shop price of £54.99 and a maker rating of about −20°C are claims attached to that circulator. They are not measurements of the Blagdon vent or the VIHOSE tubes. A heating element and a temperature knob put you back on the heater side of this page.
When is a set-point heater the wrong comparison?
When the job is a hole. The VIHOSE tubes are listed for about 60–80 and about 120–150 gallons, with a knob, and the titles also say fish tank. Next to a 5 W pump they look expensive if the knob is set warm. The 50 W vent is the heater in this comparison. The tube belongs in a small tub where you asked for a temperature.
Can I run both?
You can, if each appliance is a pond-rated device on a 30 mA RCD outdoor socket and both cables have a safe route. A vent plus a small air pump is a second way to hold a hole. You do not have to run both once one of them is holding a patch you can see. If the air pump is the IPX4 oxygenator, it stays out of the water. If the heater has no stated voltage, do not add it beside the pump.

Related pages

Pond air pump comparison

Pond heater

Best pond heater: which of these four listings fits

Best pond de-icer UK: buy the job, not the wattage

How to use a pond heater without cracking pond ice

Wildlife pond frozen: when you do not need a heater

Sources

Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the four amazon.co.uk listings captured on 20 October 2026. A missing voltage is not treated as 230 V. The Ofgem unit rate is the price cap for England, Scotland and Wales, not a household tariff and not Northern Ireland.

  1. RSPCA, pet fish in winter (retrieved 20 October 2026)
  2. RHS, ponds in January (retrieved 20 October 2026)
  3. OATA, how to look after pond fish (retrieved 20 October 2026)
  4. Ofgem, energy price cap 1 October to 31 December 2026 (retrieved 20 October 2026)
  5. Blagdon, Affinity Ice Vent (retrieved 20 October 2026)
  6. Professional Electrician, electrical installations in the garden (retrieved 20 October 2026)
  7. IEC 60335-2-55:2021 (retrieved 20 October 2026)
  8. ARC, pond FAQs (retrieved 20 October 2026)