Green algae ID on this?

[taylormaximus]

So this has been growing in my tank for about a month now, deep green patches, not really hairy or overly slimy, it grows only on the rocks, and it grows in expanding circles like green coralline algae does, except this is a much deeper green than coralline (I've had some of that as well), and also unlike green coralline it can be easily scrubbed off the rocks with a toothbrush, but it can't be blown off. When it is brushed off it comes off in large green flecks that almost resemble tiny pieces of nori. And it starts to show signs of returning after 3 days or so. I can provide water parameters or other details if needed.

Any ideas on this?? I'm thinking it's either some other species of coralline or green cyano.

 

[TX_REEF]

Almost certain it's not coralline, coralline of all colors it quite solid and calcified.

 

[taylormaximus]

Almost certain it's not coralline, coralline of all colors it quite solid and calcified.

Yeah it flakes off quite easily, and has a noticeably different shade of green. Any ideas on what it could be?

 

[ISpeakForTheSeas]

Yeah it flakes off quite easily, and has a noticeably different shade of green. Any ideas on what it could be?

Cyano, early growth of a sponge, or some kind of green algae would be my guess.

Does it baste off (i.e. if you squirt at it with a turkey baster, does it blow off of the rock)?

 

[taylormaximus]

Cyano, early growth of a sponge, or some kind of green algae would be my guess.

Does it baste off (i.e. if you squirt at it with a turkey baster, does it blow off of the rock)?

Oh I didn't realize sponges could just show up on their own. It has a bit of a slimy texture, but isn't much more than a film on the rocks.

It doesn't baste off at all, but when brushing it with a toothbrush it flakes off with very little resistance.

 

[ISpeakForTheSeas]

Oh I didn't realize sponges could just show up on their own. It has a bit of a slimy texture, but isn't much more than a film on the rocks.

It doesn't baste off at all, but when brushing it with a toothbrush it flakes off with very little resistance.

Yeah, they have a tendency to pop up unexpectedly (they have to be brought in by something, but just about anything could carry a few sponge spicules in for it to grow from).

A slimy texture in a thin film that doesn't baste off but brushes off easily sounds like a sponge to me - so that'd be my guess. Green sponges are pretty rare, though, so I'd suggest confirming that ID with a microscope and a little scrape sample.