truthfully there's no right or wrong however Cyanobacteria, also known as blue-green algae, blue-green bacteria, cyanoprokaryots, and cyanophytes, are oxygenic photosynthetic prokaryotes that possess features familiar to both bacteria (prokaryota) and algae (eukaryota). the key word being photosynthetic so the light is what allows it to grow again you dont have to turn the lights off, a diatom bloom is basicly the first sign that the water can support life or the diatoms being the first thing to come alive if it were me an just my opinion the longer you leave the lights off the more time it has to stable out as long as you have no fish or coral it really dosent matter for instant my tank is cycleing right now when its done ill prolly still leave them off for a couple weeks or a month when I turn them on ill get a diatom and my journey will begin, theres no right or wrong way its up to you nothing good happens fast in this hobby