I'd siphon it off but alternately you could turn off all flow, scrub it off then siphon it out as it settles to the bottom. I keep urchins, sally lightfoot crabs and hermits in my ssytems to help control algae.
On a seperate note your phosphate is too low, raise it up to above .03 mg/l. Research done over a decade ago has shown PO4 levels below .03 mg/l can cause phosphorus defficiency in coral restricting their ability to compete with algae and making them prone to bleaching.