Fish Dying In Pond?

[Haych]

I have read on another site (googled it dunno which it was!) that more aeriation to keep the water moving stops ice building up

i suppose you never see a frozen river!

 

[Tokis-Phoenix]

Hmmm...

1. Feeding: It is absolutely fine to feed pond fish wheatgerm pellets in the winter as this is what these pellets are designed for- their low protein content and easy digestability means that even fish with slow metabolisms in cold water can digest such pellets safely.
However wheatgerm pellets are the only safe food to feed fish during the winter. It is not essential to feed fish during the winter, however feeding small quantities of wheatgerm pellets once a day may help them through the winter.

2. The depth of the pond: This is what i think killed the fish. I have to say that 1.5ft deep is nowhere near deep enough for goldfish or koi. It is recommended that you have at least 4ft deep for koi while 3ft deep for goldfish- any shallower than this, and you risk loosing the fish during harsh winters. It is the depth of a pond that helps insulate it against the cold, and the deeper it is the warmer it will be in the depths- too shallow, and the pond will be considerably colder overall.
I hate to say it, but with the shallow depth of the pond this was an accident waiting to happen.

If you are still positive on keeping the fish in the future, i would strongly recommend that come spring you re-dig the pond and make it at least 3-4 deep (depending on whether you want koi or goldfish or both). Re-digging the pond can be a pain in the bum, but it will seriously reduce the risk of incidents like this to almost 0. The deeper it is the better- i know someone who keeps koi and they have dug their pond to 6ft deep! This is quite a lot, but there is always more benefit to having a deep pond, while always more risk with having a shallow pond.
I guess you could run a pond heater and put some sort of plastic cover over the pond during the winter, but the electricty bills for running outdoor pond heating can be extortionate and so it will definitely save you more money and effort in the long run if you just make the pond deeper .