Unknown bacteria/algae

[Derek8c]

I noticed this very dark purple almost black stuff growing on some of my rocks in certain places. When I scrape it with a brush it has a very slight purple tinge, and no matter how hard or long I scrub it doesnt come off. I couldn't find any coraline algae that looks the same online. It looks very dark almost black. Any ideas what this is? Tank is 3.5 months old

 

[Daniel@R2R Verified Admin]

I've heard of black coralline algae, but not sure about that. Any chance it's a sponge?

 

[P-Dub]

Hmmm, it does look very much like some sort of coraline algae...;Bookworm

 

[P-Dub]

For shiggles and gicks, it appears that, whatever it is, might be growing in low or no light. Am I correct in that assumption? If so, try exposing the, whatever it is, to light and see how it responds and report back. Give it some time.

 

[Derek8c]

For shiggles and gicks, it appears that, whatever it is, might be growing in low or no light. Am I correct in that assumption? If so, try exposing the, whatever it is, to light and see how it responds and report back. Give it some time.

I took these pieces out of the tank to look at them closer, that's why it looks low light. I have a 100watt light running at about 70% intensity. Theres quite a bit of light in there

 

[Derek8c]

I've heard of black coralline algae, but not sure about that. Any chance it's a sponge?

I guess time will tell