Pond depth

Question
Hi, I was wondering if you could help answer a quastion for me?  I have a pond which was set up last year and had just goldfish but I have added Ghost koi which are 2x4inches and 4x2.5 inches.The pond is only 2.5ft in depth and I'm wondering if the Ghost koi will be alright over winter.The goldfish were fine last winter even though the surface of half the pond had ice over the top but have now heard that the ghost koi are hardier than normal koi but will the pond be too shallow for them to survive the Scottish winter?? it does have a waterfall that is running 24/7 obviously the side of the pond where the waterfall is doesn't freeze so should that help?? Many thanks

Answer
Hey Amanda, two things, first ,running a pump all winter is hard on the pump. The shaft in the pump is ceramic coated and if it cracks it will ruin the pump second I use a trough heater that farmer use to keep there trough from freezing. Its about $30.00 and it only comes on when it gets down to 30 degrees. Hope I helped. Remember don't get to many fish in your pond, rule of thumb you need about 3 gallons per fish. Yes 2.5 feet depth should be fine Thanks Eric