Okay, need help with this, What is it and how do I get rid of it?

[RSargent1]

This just started this week and there are no fish in this tank, a sand sifting star, a couple of small hermits, and some small soft frags. Params appear to be okay, It's a 5 gal only and I've addressed the phosphate issue although maybe a little too late. Any ideas?

 

[Genesis Corals]

Check out this guide: Nuisance Algae ID Guide

 

[Reefing Madness]

Possibly the start of Dinos. You get a new frag recently?

 

[Mike J.]

Looks like dinoflagellates. Need to nip it in the bud right now. Siphon it out every day, don't blow it around. Remove all detritus that you can find. Go ballistic on keeping your tank clean or it will take over.