What is this black stuff?

[Abby B]

I have a 29 gallon tank in my preschool classroom that had been set up for around 4 years.  A couple of months ago I had to replace the tank because it got a crack in the glass (preschool mishaps) and decided to change out the substrate and add some more plants while I was moving everything.  A little while after moving everything into the new tank I noticed this black stuff all over the place.  It seems to be concentrated mostly on the edges of the plants (particularly the anubias), but it's also on the substrate and decorations.  I'm not sure if it's algae or something else.  I tried removing it by hand, but it wouldn't come off.  My otocinclus and pond snails don't seem to be making a dent in it either.  The new growth on the plants doesn't have any black on them. 

So my questions are: What is this black stuff and how do I get rid of it?

Edited April 20, 2021 by Abby B
Add pictures

[OnlyGenusCaps]

Does it look fluffy?  Like this?  If so, it's called black beard algae.  It's a contaminant on plants and other things that stay wet.  Your tank has been infected.  Sorry. 

There are ways to control it with hydrogen peroxide, to which it is very sensitive.  Some try lighting and nutrient tricks.  I just tore down an aquarium that got infected, sprayed everything with peroxide, and am reworking the whole thing.  I feel this is easier than constantly dealing with the stuff. 

If this is what it is, don't buy plants from the same place.  It's a likely source.  Good luck!

Edited April 20, 2021 by OnlyGenusCaps
Black beard algae not "black bear algae"; although...

[Colu]

You can spot treat with seachem flourish excel to help get rid of black brush algae just be careful not to over dose 

[Abby B]

It's not really fluffy or fuzzy at all.  It's pretty smooth.  I've been searching for what it could be and came across black beard algae, but that doesn't really look like what is in my tank.

[Colu]

6 minutes ago, Abby B said:

It's not really fluffy or fuzzy at all.  It's pretty smooth.  I've been searching for what it could be and came across black beard algae, but that doesn't really look like what is in my tank.

It looks like the start of black brush algae to me looking at the pictures

[tolstoy21]

You can do a weak bleach dip of the anubias to kill it on those plants. Plenty of tutorials online on how to do this. I’ve done it a few times and works well. But whatever is currently causing it will also need to be figured out or it might reestablish itself. I’m not a guru on the  topic of algae, but that stuff plagued my anubias when my tank was settling in.