Aaah, what a pleasure to get rec.ponds again without the disturbed
commentary. Many thanks to those who pulled it off.

Our pond is 3 years old, 400 gallons, 30" deep, partly shady, 6
goldfish and 3 koi who are ~6" long. We're in San Francisco, moderate
weather.

Some perplexing new changes lately: 1) Fish seem scared. 2) String
algae has arrived.

1) In the last 3 weeks the fish have been hovering near the bottom,
seemingly scared. This was never the case; they'd always swim around
the top, especially during feeding. Now they won't come up at all.
Of course they could be terrified of the Great Blue Heron we saw on
the neighbor's roof 2 weeks ago (said bird then flew over to the
flimsy tree above the pond, though the bird never went down to the
pond as we watched). The heron could be visiting when nobody's
watching, but no fish are missing. It's a small, enclosed yard; I
doubt the heron's visiting that much. Could something else be the
problem? I water tested last week and everything's normal. Not only
do they hover near the bottom, I've seen them so low sometimes they've
got dirt/mud on their backs. Any ideas? Is this some weird spring
ritual? Or, is it related to...

2) String algae. We never had it before. Crystal clear water, in
fact. No big change in amount of sun. What causes this stuff. Maybe
I should leave it so baby fish & frogs can hide in it. Does it bother
fish? Can they get caught in it? Do they like it? Can I get a kind
of fish that eats it? I've got alot of elodea growing in there.
Thanks for any help.