if the sand you're using have dead stuffs in it, then you'll have a mini cycle. since you don't have anything in your tank yet, you have nothing to worry about. be patient on stocking the tank. research first before you buy anything. i would not put the chaeto in the display. if you have a sump, chaeto can go in there. you can run the lights but you'll have algae. one week is too soon for fish and corals. i would wait a couple more weeks, then test ammonia/nitrite/nitrate, do a water change because the nitrate will be high, and finally try some clean up crews. in the mean time, set up a quarantine tank and quarantine fish/corals. btw, you need to have some type of filtration system set up to export nitrate, phosphate, etc. i'm talking about skimmers, algae scrubber, gfo, refugium, etc. good luck!