Orange growth on rock

[Sidman74]

Any ideas what this is? Appeared out of nowhere.

 

[54seaweed]

looks like Coraline algae starting to form , I've seen it in red , purple , orange , yellow and blue sometimes even in white , it is harmless nothing to worry about ,

 

[Reefing Madness]

Looks like sponge growth, see if you can just wipe it off. Won't hurt anything either way. New tanks with high phosphates will grow them more than others.

 

[54seaweed]

that don't look like any sponge I've ever seen

 

[coralbandit]

That's a sponge or tunicate IMO.

 

[Sniperhank]

If it is hard it would be a type of coraline algae.
If it is soft it is probably the start of a sponge growing...though you don't typically see them growing like that right out in the bright lights but will find them in the shaded areas most of the time. There are exceptions to this rule, but those sponges are rare, but beautiful.

 

[Istrom]

I don't think it's a sponge, most sponges have a clearly visible choanocyte.

90 G Reef
55 G Discus
24 G Reef

 

[Reefing Madness]

 

[Sniperhank]

And those are the sponges I'm referring too. They are beauties.