You don't always have to know how to heat a pond in winter. In fact, for many gardeners, it won't be necessary, even for those who have a few resident goldfish or koi.
For starters, these cold-blooded fish are winter hardy, so they can cope with cold temperatures and the odd freeze as long as there's enough oxygen. This is where a de-icer can come in handy – even just melting a hole in the ice with warm water can do the trick.
