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.