Smallpond,

I have bluegill morts every spring and it comes and passes just as Bruce says. The algae could be something that attaches after the fish dies as the surface of a fish is rich in nutrients. Sometimes however spring morts are a sign of too many fish in the pond. With too high of carrying capacities the over all fish population is not getting enough to eat before the stressful winter. It's nature's way of culling the numbers.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.