Greetings all...have a little problem with my goldfish. Briefly:

We set up an ornamental pond about a year ago and stocked it with 7-8
of the 26 cent goldfish from walmart. To our surprise they thrived in
the pond and all even made it through the winter. Last night, as
always, I went out, shut off the pump/fountain (this is their dinner
bell and they all know to congregate in the "feeding cove" ) Threw in
a couple dozen food pellets and watched them dart around in their
normal happy feeding frenzy.

Tonight was a different story. I noticed that there weren't any fish
to be seen when I walked up to the pond and as I stopped the pump and
tossed in the food, nobody came to the top to eat it. I watched for
several minutes and still nothing? After a bit longer I got the
skimming net and tried to go "fishing" I just caught a glimpse of one
fish darting off into the depths but nothing else.

Some specs about the pond:

2 feet deep in center (about 3'x7' area)
12-16" deep ledge (about 9'x14' area)
water temp is 77F, 25C
we have various aquatic plants...lily pads, water lettuce, hyacinth,
grasses, etc.
it has a filtration pump that runs 24 hours a day at 500GPM

The pond has had a bit of an algal bloom this spring...water has a
green tint and about 1 foot visibility, but I was hoping the plants
would help and haven't added any chemicals.

The fish have seemed to be quite happy for the past year, now, out of
the blue, nothing?

Any help would be greatly appreciated!

Thanks
Corey