I run the fCE4800. I’d normally tell you with out a doubt 100% but you can get away with 75% if you really know what height to have it at.. cuz this thing has excellent photon distribution. IF you’re trying to save money. You could run as low as 75% at maybe 10 inches. If not, just go 100% at 15-18 inches, drop a bit lower if not showing any issues after a few days