In the short term, a frozen pond (or more precisely its surface), will not pose any problems for the health of koi. Koi and other pond fish will naturally descend to the bottom where, if the pond is of sufficiently deep (4 feet is the minimum desired depth, although many shallower ponds can overwinter their fish surprisingly well), will allow the frozen conditions on the surface to pass unnoticed. They will have been preparing for this event over the proceeding weeks and months with the shortening day length and dropping temperatures signalled the onset of winter.
If a garden pond, which compared to a natural water body is likely to be more heavily stocked, is allowed to freeze uncontested for more than a few days, then as time passes, the risk of problems beginning to arise starts to increase.
Winter Pond Advice.
All you need to know for your pond and pond fish to survive the harshest winter in a garden pond.
Winter Pond Information Centre: Overcome ice, frozen ponds and freezing weather safely.
- Winter pond care and winterizing a koi pond. How to take the steps before, during and after winter to keep your pond and fish safe.
- How pond heaters work. Top guide on the different types of pond heaters.
- Survival strategies for a pond and fish over winter. Beat the challenges of a frozen and icy pond this winter.
Despite the phenomenon of global warming, whether real, imagined, man made or of natural causes, there is still a real possibility of suffering some extreme cold weather over winter. Besides being the stuff of picturesque Christmas cards and memories of fun in snow and ice in the playground, ice can pose a real threat to the health and well-being of a pond and its inhabitants.
Natural water bodies such as lakes and ponds will freeze regularly throughout any typical winter and appear survive the experience with little impact on the fish or other aquatic life. So why bother to take on Jack Frost when he decides to visit our own garden ponds?
Well in the short term, a frozen pond (or more precisely its surface), will not pose any problems for the health of koi. Koi and other pond fish will naturally descend to the bottom where, if the pond is of sufficiently deep (4 feet is the minimum desired depth, although many shallower ponds can overwinter their fish surprisingly well), will allow the frozen conditions on the surface to pass unnoticed. They will have been preparing for this event over the proceeding weeks and months with the shortening day length and dropping temperatures signalled the onset of winter.
If a garden pond, which compared to a natural water body is likely to be more heavily stocked, is allowed to freeze uncontested for more than a few days, then as time passes, the risk of problems beginning to arise starts to increase.
An ice-capped pond is prevented from enjoying the normal gas exchanges between the water and atmosphere. Even when water temperatures are low, fish still continue to metabolise, requiring oxygen and releasing CO2. There will also be limited amounts of CO2 and other non-desirable volatile products released by bacteria and invertebrate life as they work on and break down a range of accumulated organic matter. As these gases accumulate, they can reach levels that can affect water quality, making it turn ‘sour’. A build up of such gases can also inhibit fish from excreting similar toxic gases from their bodies. So we should ideally look at ways of allowing gas exchange to take place.
Ponds that freeze over is an inevitability for the majority of us, as only a minority of koi and garden pond owners are blessed with the foresight or means with which to heat their pond. Large scale pool heaters, which heat the water as it is pumped and recirculated through the filter system (swimming pool style), can be expensive to purchase, install and run. So how do we lesser, non-heating, pond keeping mortals manage the problem?
Short term measures As already mentioned, there is no need to treat a frozen pond like a failed pump, or a leaking pond, as fortunately, time is on our side. If nothing else, to ease your mind, thaw a small hole to allow some gas-exchange by pouring some boiling water on to the ice. Ice should be thawed quietly, without banging or breaking the ice with physical force as the pressure waves and noise can shock the koi’s sensory systems by stimulating their lateral line (their sixth sense which detects pressure), and their ear. (yes, koi do have ears!). Any noise that you produce is an unnecessary shock, as the koi and other pond fish will be so lifeless, that they are likely to be oblivious to the presence of ice several feet above their heads.
Long Term If the cold weather proves to be part of a longer freezing spell, then a more reliable and labour-saving method to prevent a total ice cap from forming is required. Probably the most effective and reliable method of providing a hole in the ice for gas-exchange is a small, inexpensive pond heater. Sold with a float, the pond heater (usually 100W) gives off sufficient heat to provide a hole in the ice, with the same running cost of a standard light bulb. Because of its low energy demand, it can be installed using a standard extension cable, protected with an earth leakage breaker. Like most effective solutions, it is cheap, straight forward and simple to use. This is more reliable than other innovations such as footballs and other polystyrene space-like devices that can have a tendency to become frozen in a solid ice cap.
- Feed pond fish and koi safely in winter and autumn.Fish digest and use food differently in autumn and winter.
- Heating a pond in winter. A frozen pond can harm your fish.
- A frozen pond in winter, covered in ice can kill your fish. The best way to keep your fish alive through freezing winter temperatures.
- A pond in winter as it moves to spring needs special care.Careful pond maintenance from winter in spring will give your pond a good start in the spring.
