my tanks about a month and a half old. i got some green hair algae and still some brown diatoms alot on the back glass. just tonight i started scrubbing the back with a toothbrush to clear some of the algae and i have two very small dots that the toothbrush does not disturb. they are whiteish purple. i have been doing alot to incourage coralline i have many little pieces of rubble with it on it and i regularly pick them up and scrape at them infront of a powerhead. i think my goal of growing coralline is finally starting on the back glass!