I've got a 400-500 gal pond with a 3ft waterfall. Its finally up and
running with plenty of plants and prob too many goldfish(21). The only
problem (other than maybe overstocking) is that I have very little
sunlight.
I want to expand to a second pond and am wondering wether they should
be connected for a larger total volume, or two separate ponds to keep
cross contamination to a minimum.

Fuzz