What are these?

Saw them in my friends tank and we both have no idea!

 

Looks like flatworms. What are they on and what ist the orange?

 

They are on the glass and rock... The orange is the paint on Thier wall lol

 

Two copepod-eating flatworms plus a whole bunch of spirorbid polychaetes (calcareous feather-duster worms). Neither are harmful.

 

just a thought - they look like pineapple sponges. harmless filter feeders

 

I was thinking that as well.

 

Not pineapple sponges, flatworms.

 

Definitely the copepod eating flat worm! Fast moving. Produce sexually in mass numbers and also by splitting themselves in half, YUCK!

 

The flatworms in the image are usually harmless and numbers are usually self regulating. This is not a flatworm that has population explosions.

In my experience with this type of flatworm, there are usually a few hanging out and never have been an issue unlike Red Planaria.

There are hundreds if not thousands of different types of marine flatworms, not all are harmful or require intervention.

 

Ok thanks guys ill let him know