Plants, plants, plants.

You have been given lots of good advice. Fundamentally, the algae is
growing on the nutrients from fish waste, etc. It can't compete with
vascular plants, so plant lots of them! You could wait out the
bloom. That would not work well if the fish are producing loads of
waste. Can you add some stuff like hyacinth?

A UV filter will kill the algae for you. We run ours at the start of
each year before the vasculars get going. Then we turn it off.

Jim