I've been in a struggle with brown dusty (glass) & hairy brown ( live rock & corals) and rusty crusty on glass since last Christmas when I was gone for 14 days. Prior to that my parameters stayed stable with very little interference from me. I have the standard cleanup crew, several algae loving fish and use a scrubber in my sump, have great success with my tunze skimmer, additional powerhead, led lights and ato with ro/di and alkaline filters on my intake. I almost felt like I was over the hurdle and I went away for 9 days and blammo! Hairy brown algae on the rocks closest to my powerhead.... and this pictured conundrum. It has long purple fine feather like fronds, grew from about 1cm when I left to a healthy 2-3" when I came home... any ID on the mystery thing? My corals are thriving and I have coraline algae on my back wall. Oh, and this was new, when I cleaned out my hog algae scrubber last week, I had a bunch of baby shrimp looking life in and around the robust green algae. Is that a good thing?