Not only do I have copepods but I also have amphipods. Small 2-3mm shrimp like things buzzing over the rocks. Could them running between and over my gsp make it be closed? Guess I am going to get a Mandrin soon. I only have a 30g tank but I have hundreds of these amphipods and the glass is covered with copepods daily before cleaning. Without a refugium could one Mandrin wipe them out? A fuge is in the future.