Thank you for your sharing your knowledge with us, Habdab
So really then the lake is little more than a large concreted puddle, that goes stagnant in the heat. I'm sure all would agree that any fish would be happier if moved to a more appropriate environment. Although I assume the algae issue would remain a potential problem, unless the lake was extensively re-designed and altered.
(I never knew that ducks and geese pooed three times an hour though... wow, the things you can learn from this little forum....!