I recently finished making some minor modifications to the ponds, most notably creating more level bases to the ranchu ponds. Doing this has improved the drainage and cleaning procedure for me when the ponds are syphoned. The liners all came out and 50mm polystyrene sheets were placed across the bases. The soil beneath the sheets was levelled, with a minor slope created from back to front, which now pushes water to one end of the pond when emptying. At that end a small, deeper, drainage section was cut out of the polystyrene. The results have been great.
The weather is meant to turn colder over the next few days, with daytime temps set to go from around 18 degrees C to around 10 degrees C. The reds of autumn have come out in plants around the garden in the last couple of days and i'm now thinking this might be a good trigger for beginning the wintering process of my ranchu.
Today i learnt something promising about the effectiveness of my ranchu pond lids. I have two ponds full of water, the one the fish are in, with a heater, has sat with the lid open today. It has been a cool overcast day, the unheated pond (without fish) has had the lid shut and when tested was 3 degrees higher than the pond with ranchu in. The heater has also been on at times to maintain the set temp meaning the lids are adding at least 3 degrees C to the ambient water temperature.