Black spots growing on my rock

[chemicals]

Hi,

recently I noticed some black stuff started growing on my rock. The thanks is around 6 months old. Should I worry? It’s pretty hard to the touch but feels more “slippery” than coralline.

 

[KrisReef]

Normal, and nothing to worry about. I don't know specifically what you have but it will come and go as the tank matures.

 

[90's reefer]

Looks like black sponge to me.

 

[chemicals]

Looks like black sponge to me.

Should I try to remove it or just let it sit?

 

[KrisReef]

Should I try to remove it or just let it sit?

Sponges are good part of a balanced ecosystem. I try and collect rocks with sponges from others tanks to add to mine to increase diversity.

 

[90's reefer]

Should I try to remove it or just let it sit?

Leave them in. They wont harm anything.

 

[WheatToast]

Possibly also a harmless red encrusting algae like Hildenbrandia or Peyssonnelia, but it's hard to tell without closeups.

 

[chemicals]

I took a sample and put it under a microscope. I don’t think it’s a sponge, but my next guess is that it is some kind of cyanobacteria or something.

 

[chemicals]

Possibly also a harmless red encrusting algae like Hildenbrandia or Peyssonnelia, but it's hard to tell without closeups.

This could also be an option, the square cells kinda resembles them. I’ll keep an eye on it! Thanks for the responses!

 

[vetteguy53081]

Looks like Ircinia spinosa which is a dark sponge like substance and should be removed as it contains toxins. Take the rock out and place in container of tank water and inject with vinegar and take a dental pick or small crochet needle and pull off and discard