I have a 400 gal 'pond' for a waterhole for the critters on my
property. I can't keep the damn frogs from fornicating in it and
loading the pond with hundreds of tadpoles. With them comes nasty
pond scum (suspended algae). Anyone have an idea on how to control
the frogs and still have the water safe to drink for the animals,
dogs, & bees?

Pond is lined, with sand covering the liner to protect it from deer
hooves. No electricity nearby for an aerator. Bleaching, draining, &
refilling only gives a temporary fix. I'm suspecting frog slime
holding the eggs until they hatch is the likely cause.