Wasn't there a kids book about an old woman who swallowed a dog to swallow a cat to swallow a rat to swallow a snake that swallowed a frog when she accidentally swallowed a fly?
The fish should help take care of the frog problem. Those frogs are probably eating something, though, so maybe there is a mosquito or gnat problem they are helping out with?
Ponds in full sun tend to collect algae. If you're planning to grow aquatic plants you'll need about 6-8 hours of sun a day, but no more, so you could plant some evergreen type material around it that isn't too messy.
Water lilies will also help to block light entering the pond, as would some hyacinths or taro plant if your filter is the open kind. They consume a lot of the nitrogen in the water that the algae would need to bloom
So if you reduce the sun, and the nitrogen (ammonia), circulate the water, and add some plants to compete with the algae, things should improve.
Regards,
Matt