Yes, I've used a UV to deal with green water algae bloom in newly set up tanks. Green water is really the only algae a UV clarifier is effective against. Doesn't kill it, just coagulates it into large enough clumps so the filter can remove it.
It clears the water very quickly (within a day) but doesn't address the underlying cause. Once the plants are established and growing well though there shouldn't be any need for a UV any more, except maybe to control a disease outbreak like ich amongst your fish.
I've also heard UVs oxidise much-needed iron out of the water, and my own testing pretty much backs this up (as much as standard Fe tests work, or don't), so you'd have to dose Fe daily each morning after switching the UV off and so have it running only at night.