Blue Water From Yellow Sponge Looking Stuff???

[BSJF]

Been on my mind. Just curious what this was and what causes it. I'm assuming it is a defensive reaction, but don't know.

I removed a ton of rock from my tank last week. I get yellow sponge looking stuff growing all over my rocks and proceeded to scrub it off. The water turned blue like ink from broken a blue pen in the water.

Anyone know? This is rubbery feeling stuff, so may not be sponge. Turns black when dry.

[Kristy]

No idea.

But I do have a couple spots of "sponge" (presumably!) that are more slick and rubbery and it is very hostile to corals, will grow over them and smother and kill them. Sponge is typically more porous, delicate, fibrous, and, well, spongey for lack of a better description! I have it in a couple different colors - not yellow - and in two different tanks. Wonder if this is the same stuff? Can you get a picture of yours? I could maybe try to get a pic later but I've tried to peel away most of it now that I realize how un-friendly it is to coral.

[BSJF]

lol, just look at about any pic of my tank and you will see it. It doesn't peel off easily unless it is on a smooth rock.