Algae question

[Alex mosco]

I have tried taking the algae out via siphon, pressure cleaner, red slime remover. Nothing will work, i dont even know if it is cyano. HELP, WHAT IS THIS!?

 

[AntarcticIkeelu]

This is probably a stupid question but it's not that black stuff right, that's just the rock?

 

[Alex mosco]

This is probably a stupid question but it's not that black stuff right, that's just the rock?

All that black algae is on a rock, this is what it looked like after i sprayed it with a pressure washer.

 

[AntarcticIkeelu]

I have no clue then, definitely following along would love to find out what it is.

 

[BlueCursor]

Do you have any pics of when it was still in the tank? It could be black sponge, but out of the water I can't be sure. I have to go with black sponge based on what I see, though.