I've had my present 75 gallon tank up and running since February. It has live rock, a cleaner shrimp and a royal gramma, some hermit crabs and a few turbo snails ( I'm going slow). There is no hair algae. I do have what I think is a lot of pretty purple coraline algae. It has recently started to develop this brown and reddish brown algae :?: on the substrate. What kind of algae is this? Is it good or bad? :? I've been mixing it deeper into the substrate with my fingers because I think it's unattractive. What should I be doing? Is there a reason this started to appear?