I’d of algae or sponge
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- Thread starter steezreefing
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Ron Reefman
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Tampa Bay Reef Keepers
MAC of SW Florida
Really hard to tell from that photo. Have you tried touching it? Or scrape at it with something pointed (I use a dental pick). My best guess from the photo is a sponge, but then most black sponges don't like light and tend to grow under rocks. Is this new growth or could it be an old rock used in a new setup and this was the underside?
