"Rodney Pont" wrote:

Hello Rodney

I did seriously consider CH pumps, but the plumbing got a
bit complicated and the corrosion issue was a big one I
think.
RP I've just seen an advert in Practical Fishkeeping for a
RP plastic impeller for Grundfos CH pumps so that would solve
RP the corrosion problem. I suspect that with the price of the
RP conversion they are more expensive than a proper pond pump
RP though.

I think you're right. I do like submersibles though, so much easier.
With an external pump, which seem to be preferred in America, you need
a dry chamber next to the main pond which is below water level so it
self-primes. Tricky to seal effectively, especially with wildlife type
ponds.

--
Simon Avery, Dartmoor, UK Ý http://www.digdilem.org/