UV system for pools?

[vinper]

they use them on koi pond alot to control algea , supposseddly they make algea clump so the filter can pick it up

[PoolDoc]

Unfortunately, there seems to be ZERO evidence that that actually helps, at least in pool situations. Since full summer sun includes light in the wavelengths I'm aware of in UV reactors, if the UV reactor could 'clump' algae . . . then sunlight would do it, too.

Also, 'clumping' live algae, at least with pool filtration, is of very questionable value. Live algae -- clumped or not -- tends to pass through a sand filter, and tends to stop up DE filters, very rapidly.