I'm not sure adding copper wire balls actually does anything to get rid of algae... there shouldn't be algae in your aquarium to start with if you are keeping it properly clean.

Copper does keep moss off roofs but I think it would act as a poison in an aquarium. Green stringy algae in a pond can be removed with a child's fishing net but when the pond gets properly balanced the water should clear. It can take at least 12 months .Do not try to deal with it by changing the water or you'll be back where you started.
How big and how old is the pond?

Don't do it.

Copper is harmful to fish and will kill all invertabrates. I've used a copper treatment for whitespot (Cuprazin) in a tropical marine fish only aquarium and it has to be carefully controlled.

Some algae is beneficial to the aquarium. It's a green plant so it takes up nitrogen and releases oxygen into the water - good for fish. It helps to stabilize the PH and also a food source for fish & turtles.

You can control it in an aquarium to some extent by adding some snails which will trundle up and down the glass eating it.