About three years ago, I put regular and gold WCMM into my pond in Worcestershire. The golds are still alive, and the pond has frozen over, but there is a lot of planting. The sides of the pond are insulated with polystyrene tiles to prevent too much freezing, as the sides are wooden and elevated about one foot above the ground.

The only disappointment was they had never had eggs, but the pond is loaded with newts, louse, and leeches which may have stopped that. It's now aerated and has a solar waterfall.