Seems a bit long winded but yes it would work, daphnia eats algea, We had an old rain water tub behind our shop that we kept our daphnia in, the natural algae in the tub kept them alive, they breed like wildfire, this tub kept our shop in stock for years, and cost nothing to produce.
Any tub with green water that has been left in the garden, buy a small bag of daphnia put it in, forget it until you see lots of movement, get a net scoop some up,,,instant nourishing fish food.
If you find the water is losing it's algae levels, throw a cabbage cut into quarters in the water they feed happily on that, plus the cabbage induces more algae to grow.
By the way use a fine net and run the caught daphnia under the tap to get rid of the stagnant water.
Have fun growing daphnia.