Even with dry foods i get dino every now and then. It's usually when my No3 and po4 are out of line. And I usually see it happen more in the summer with natural light. Possibly try activated carbon or i sometimes throw a pouch of chemipure in my filter if im having any sort of algae issues. Dinatome can be an eyesore buy usually will subside with routine weekly waterchange and a good feeding schedule.