ID This!

Yes they are indeed flatworms. There thousands of different types.

The issue with this type is population explosions. They begin to cover corals, some types are parasitic to corals, others cover so much of the corals like mushrooms that they inhibit both penetration of light and gas exchange.

Some are photosynthetic and a black out or reduction in lighting can limit their numbers.
Others require chemical treatment such as FlatwormExit (some are resistant)to effectively treat.

You can also try the natural method of addition of some types of Damsels and Wrasses but there is no guarantee that the fish will consume the FW's.

Melevsreef.com - Pest Flatworms
Melev's Reef - Visual Identification

 

My melarunus wrasse ate all my planaria flatworms in 5 days. Just a though. If you want one try to get a male they seem less aggressive.

 

What type of damsel would be my best option (Chromis, blue, yellowtail, white/black ones?)? I'm hesitant to add another fish to my system after losing 3 clownfish to ich. Losing a cheap damsel to ich ich, losng a pricy wrasse to ich is another thing.

 

Sorry for the persistence. going to buy one today, just need to know best type.

 

The pic is pretty fuzzy, but I suspect they're Acoel sp. which feed on algae, detritus, and copepods.

There's an off chance they could be Amphiscolops sp. which feed on copepods, but just going by the pic, the shape seems to fit Acoel better.

Take a look at this PICTORIAL HITCHIKER GUIDE and see if your FW is there.

 

Thanks! They are Acoel fw. Do Damsel fish eat them?

 

Not that I've ever seen...I've seen leopard wrasses eat them, as well a mandarins (greens moreso than blues). There are several small wrasse species that will eat them.

Velvet nudies will also eat them with great gusto (exclusively).

 

How susceptible are green mandarins to ich and what can u feed them when their supply of fw are gone?

 

After thinking about some things and talking with my LFS, I have decided to let the worms be for now. Paying $50 for a nudibranch that will be in my tank for a limited amount of time and possibly dying isn't worth it (the same can be said with buying a wrasse with my recent ich issues). Instead, I am going to give my rocks an RO bath and siphon out the remaining worms when I move (2 months) and upgrade from my 20 to my newly purchased 55 gallon.

 

spend $20 now and use flatworm exit and get rid of them. I have never seen any type of damsel eat these.