What Are these? (Pics included)

[desertduck]

My tank is about a month old and still cycling, but these popped up yesterday. What are they?

 

[TheEngineer]

Appear to be hydroids.

 

[desertduck]

Appear to be hydroids.

Aren't hydroids a type of pest jellyfish?

These things just kind of stick to the wall and don't move at all

 

[Katrina71]

They usually die off. Common in a new tank.

 

[reef lover]

Medusa hydroid

 

[TheEngineer]

Aren't hydroids a type of pest jellyfish?

These things just kind of stick to the wall and don't move at all

Indeed they are! This type attaches to the wall.

 

[John A!10]

Medusa hydroids