Ive had my tank cycling for several weeks and I just added fish. At this point, I'm nearing the first water change time. My question is this. Coming from a freshwater background, I usually vacuum the gravel a little when I do water changes. Should I do this with the Saltwater tank? I have sand down on bottom.

you should not have any thing settel on top of the sand. if you have some spots of debries on the sand you should get it out and try to corect the probelm. it will collect bacteria/ witch can cause red slime/algea . proper water flow will channel nutrients to filter feeders/ protien skimmers and filters. dead water spots will lower ph in that region as well as cause algea .