Will these goldfish eat algae?

(Photo by Kathleen Rolfsrud)

That PVC pipe in the background is connected to a water pump. (It's not a submarine.)

We've introduced a bag of goldfish to the pond to see if they can join in on the efforts to clear the algae and debris.

Before. Satellite view from last summer.

From a satellite, the association pond is a disaster, it shows up green from shore to shore. We've tackled it with aeration, dip nets, raking and other methods, even getting the waterfall started again after a five year hiatus. We figure we've manually dumped out 100 pounds of algae so far. It's great exercise.
There's a "thermocline" in the 10 foot deep pond, which means oxygen doesn't go to the bottom, so the anaerobic bacterial action there is creating muck and sulphur gas, which smells like rotten eggs when disturbed. We hope to reverse that with aeration, lifting the oxygen deprived layer to the top.
We've lost track of the goldfish, hope they'll turn up again. Sometimes you can see ripples where we think they may be. There are a ton of frogs and turtles moving about, so we know the pond can be restored, but algae can bloom overnight, it's tenacious. Hope the turtles didn't eat the fish.
Koi, goldfish and other carp will eat algae, we're told, but we don't know how much. We hope this batch will survive the winter under the ice, along with the amphibians. The pond water does not drain into any protected water body, so we're good with the carp family of fish.
If we should ever attract an egret to the pond, we will know we have succeeded in clarifying the water and providing an attractive school of fish.