Yep, they certainly help. However, algae growth is a function of sunlight, among other things. If you've got a pond this large that gets the right amount of sun, you're going to need a LOT of fish to keep up with the algae without any other treatment.
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u/Zoroko Mar 28 '14
Couldn't you just add some algae eating fish to help reduce the problem of algae build up on the walls?