"Bob Hobden" wrote
"CorporalJones" wrote ...
Was it in this NG that I read that with ponds it was no longer required
to clear a hole in the ice to protect wildlife.
Followed that recommendation and ended up with multiple floating frogs
and goldfish.
So much for the experts!!!

That usually only happens if the water quality is nasty (high nitrite
content), oxygen levels low, and lots of rotting detritus on the bottom
leading to gasses of decomposition. A saucepan of boiling water placed on
the ice will thaw a nice round hole allowing the gas exchange with the
air. Never break a hole as the shock wave can kill and injure fish.


and you can always do what I do and keep your external pond filter system
running 365, but at low speed in winter, so water is always circulating.
Running water is less likely to freeze especially as the pump will create
some heat.

BTW There are kits at fish keeping outlets that you can use to test your
water quality, it's the test for nitrites you want, which will point to any
water quality problems that need addressing for the future.
The Tetra test kits work well but some with colour wheels can be a bit
expensive although they last a lifetime.
--
Regards
Bob Hobden
W.of London. UK