Black algae id/solution?

Bob2bob · Oct 15, 2018

I have this little black spot that has been growing in my 75G for a little bit. Not sure what it is and beginning to get concerned. Don't have any other algae issue's outside of struggling to get my chaeto to take off.

Tanks had livestock in it for 100 days and went through a 90-day cycle before then. I have chaeto in my sump though it's not growing super great, certainly not dying either. I use two Rapidled Corona's at about 50% intensity for 8 hours a day (algae sits in the middle of the LEDs on a rock around 15" below the LEDs). I have a lawnmower blenny and emerald crab that don't seem to touch it.

The black algae stuff is not growing super fast but has about doubled in size in the last month from a quarter to two-quarters size. To touch its a bit slimy and I feel like I can scrub it off if I need too -- though I'm worried about releasing it all over the tank.

Thanks in advance!

Here's pretty much the same photo with some different camera settings (tank LED's are off)

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Reefing Madness · Oct 15, 2018

Looks like a new piece of rock, not enough bacteria on it yet from the looks of it, take it out and scrub it off.

Bob2bob · Oct 16, 2018

Thanks for replying @Reefing Madness. Rocks about 5 months old. 90 day cycle and then 101 days now with fish in the tank.

I unfortunately can't take the rock out because I glued my rock together and this is a huge piece with a bunch of corals attached. Is it ok to scrub it off in the tank? I could do it and then do a water change right after.