From what I've read here and on the Internet I think it's brown diatom algae. I'm currently switching the lights on for about 7 hours per day. Should I reduce it and to what amount ?
Four hours is the shortest photoperiod you should do, but whether you want to work up from that or down from where you are, at 7 hours, is up to you. Either way, you just need time to get the feedback.
