What are these?

[Dalyreef]

There are two or three locations where these are growing are they harmful? what are they?

 

[ScottR]

I’m not sure what you’re asking about in particular here. If it’s the red, it’s most likely cyano bacteria.

 

[Lovemyreef2015]

If you are talking about the white string coming out of the rock it looks like sponge. Harmless filter feeders.

 

[Dalyreef]

I’m not sure what you’re asking about in particular here. If it’s the red, it’s most likely cyano bacteria.

Apologies its the Black and white sticks at the bottom of rock I am concerned about.

 

[Lovemyreef2015]

Hard to tell from the picture but they could be spionid worms

 

[Eagle_Steve]

Hard to tell from the picture but they could be spionid worms

I agree hard to tell but if the base looks like a tube of your sand bound together, it would be spionid worms.

 

[ScottR]

Now that I see it, could be spionids. Do they have two antennae-like things poking out? If so, probably. They’re not that bad but hard to get rid of. Can populate more than you’d wish. One of those things I’d rather not have

 

[ScottR]

Btw, can you get a better pic? I’m horrible at photographing aquariums. ~not the right equipment