What is this??

[Booger McMoron]

I have found these in my sump. They are stuck pretty well to the glass surfaces.

 

[Crabs McJones]

Pineapple sponges. Very common to find in the sump and overflows harmless filter feeders

 

[Booger McMoron]

Whew! I’m new to this and was beginning to panic. Thank you!

 

[SHNICI]

Whew! I’m new to this and was beginning to panic. Thank you!

you don't have to worry about, you can see them often under LR too and in sump or overflow area. feed on detritus (in the water column) and other small particles in the water. They are soft and a bit hairy, you can easy to take them out, but there isn't a reason for.
(if you have new setup/build and you are still putting new stuff in the tank, often you will see unknown creatures/algae..., you are always welcome to ask here for ID, here are many good people which will give you the help about )


Regards: SHNICI - Georgi