Critters in the overflow

[ShilReef]

Just spotted that my overflow box is filled with these little guys. Any idea what they are. Don't have any sign of these in the aquarium or sump... yet..

 

[ISpeakForTheSeas]

I assume they’re sponges - very shiny, harmless sponges.

 

[Janet Belanger]

At least some of them look like pineapple sponges to me. Not harmful in my experience.

 

[ShilReef]

Great, thanks