found brown algae coating rock, can’t be scraped off

yanni · May 1, 2022

Hey everyone!

Had this tank running since January, and have only just noticed how large these brown algae spots have gotten. They were originally quite small, thought it may be diatoms, but I’ve attempted to take the rock out and scrub them off, as well as peroxide them, but they stay persistent. The ones on my main rock scape I can’t scrub outside the tank, have to spot treat with peroxide in the tank. It’s been steadily growing however, and is starting to pop up more and more. It feels slimy to touch, but can’t be scraped off or easily removed. Looks similar to algae on my snails, but that I’ve been able to scrape off easily. Haven’t done a test in a week, but as follows

Po4: 0.05
Nitrate: 10
Mag 1500
Ca 420
Alk 11

yanni · May 1, 2022

Reminds me of lobophora maybe, but how do I treat that effectively? Seems so rare

TheNewGuy321 · May 10, 2022

did you ever figure this out? I have the same brown spots looks almost black on the purple rock.

yanni · May 10, 2022

TheNewGuy321 said:
did you ever figure this out? I have the same brown spots looks almost black on the purple rock.

Hey mate, turns out is was indeed lobophora algae. Can't appear in a system, has to be added to it. Mine came in on my snails I forgot to peroxide before adding. Incredibly invasive, but takes a long time to take over. I have little brown/black spots all over my rock, planning to drain tank, spot peroxide scrub, then refill, easy for me since my tank is only 75L/20G.

I had success with a collector urchin eating it, and also Naso tangs apparently are quite voracious eaters of it. Of course, make sure it's a healthy specimen. Unfortunately my urchin died, so need a replacement to pick up his slack.

I highly recommend peroxiding what you can of it, and invest in an urchin/tang (space allowing for the tang) and letting nature run its course. I'm winning the battle against it now, if ya have any questions let me know!