I wouldn't really mess with the sand. Overtime toxic gases can accumulate down in the DSB which when disturbed are released into the water column and can have some horrifying results. Just do some frequent water changes and scrub the algae off while siphoning out what comes loose. For the sand just siphon out the algae you see and you'll be fine.
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Sent from my SM-G925V using Aquarium Advice mobile app