Hard red substance on rocks

[Protodad]

I’ve had some pretty rapid growth of what looks like coralline algae but feel slick to the touch and is dark red. This stuff doesn’t come off easily and requires a metal tool to scrape it off.
I’ve ignored it in the past thinking it was coralline but now I’m in the middle of a chemiclean treatment and I noticed lots of stringy stuff coming off. Is this normal for coralline or is this something else?


Before:

During Treatment:

Any thoughts on what this is?

 

[dwest]

I’m not sure but I have seen similar red colored algae in my tank and assumed it was coralline. It was never a bad thing in my tank.

The stringy stuff looks like bacteria to me. I stay away from chemiclean so I have no idea if they are related.

Hopefully others will chime in.

 

[bxclent]

If it's hard, it coralline. If it's slimy and easy to get off, it's most likely cyano.cyano even grows on the sand, coralline does not. Hope that helps. I got through it with water changes, vacuuming and patience I used a feeding tube with a bulb on it to blow it off my corals. Most young tanks will get it. Patience is a virtue in this case.