Rusty red flatworms?

[PolypPocket]

These flatworms showed up in my macro algae tank. They seem to stay on the glass especially near the sand. I only have one coral in there, a small chalice, and they completely ignore it. They are all super tiny, way smaller than ghost flatworms. Any ideas on what kind these are and if they are harmful?

I have snails and crabs in this tank.

@EnterName

 

[EnterName]

Looks similar to Heterochaerus sp. (Page 5, Post #85)

They probably stick to the bottom of the glass near the substrate because that's where whatever they eat grows best and your algae scraper leaves a few residues. There usually isn't really much of a size difference to ghost flatworms (Amphiscolops sp.), so they might grow a bit more.

If my ID is correct they are mostly a cosmetic issue, but not a true danger to corals or other reef inhabitants. Some people say they eat copepods but I have not seen this first hand, so I'm not sure.

Their numbers grow rapidly so if you don't like them I would start an appropriate treatment very soon.

 

[PolypPocket]

Looks similar to Heterochaerus sp. (Page 5, Post #85)

They probably stick to the bottom of the glass near the substrate because that's where whatever they eat grows best and your algae scraper leaves a few residues. There usually isn't really much of a size difference to ghost flatworms (Amphiscolops sp.), so they might grow a bit more.

If my ID is correct they are mostly a cosmetic issue, but not a true danger to corals or other reef inhabitants. Some people say they eat copepods but I have not seen this first hand, so I'm not sure.

Their numbers grow rapidly so if you don't like them I would start an appropriate treatment very soon.

Thanks so much, I knew you would have a good idea of an ID.
I guess I will just leave them for now then since it’s only the tank of shame (aka crab jail) that has them. If they get out of hand and cover everything then I will consider my options.