Siphon it out during water changes. If you keep up on regular maintance it should pass. You will probably see some green hair algae sometime soon as well.
Welcome to R2R, @Pg513 it right on track. These are stages of cycling and on going reef tank algae control. Later in the tank like to will come down to cleaning, feeding to rich, and lighting to control algae.
The air bubbles in sand are from bacteria, it's a good thing, your sand bed is maturing.
Water changes help, but since we're adding corals I would suggest to start testing phospates and nitrates, and looking into a nitrate export method. Chaeto in sump is what most people run
I have seachem dinitrate in the sump. I could try to run a small chaeto in the sump. But will need to find a way to contain it in the sump i have seen an interesting way on a forum somewhere. See picture
That would, a porous container, making it out of light diffuser, you could also just tie it to a piece of rubble rock, it sorta stays clumped together as a ball when it grows.
Chaeto uses both nitrate and phosphate, so it depends on your nutrients, most people add a gfo when their nitrate decreases but phospates are still high.
For lighting you could do with those reptile clamp fixtures, or Home Depot has them too, and a 5500k bulb. A outlet timer and have it running 18 hours on over night preferably .
But Chaeto is just one of the solutions, cause it would solve your future algae problems, and you would need to keep nitrates down either way for your corals so it's why I brought it up.
I use an algae scrubber and love it, but not many do these days, you could also do biopellets, there's many options.