I agree with Chris. Snails, frogs, and daphnia will volunteer. Crawdads could be good, IF they are the right species. I can't recall anyone mentioning koi used for algae control - only as ornamentals (OK if that's what you want them for). Whether 50 # of fish food is a good deal or not depends on the feed and the price (and if you intend to feed, of course).

Note that I stocked 100 Bullfrog tads in each of my ponds, but only for the Bullfrogs' sake.

"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
[Linked Image from i.pinimg.com]