Brownish flatworm good or bad?

[ChuckTownReefer]

I have noticed an explosion of these little flatworms and all my corals are and have been doing great. But just want to be sure they are nothing to worry about. I will be getting either a sixline or a mandarin to help keep numbers down. Can anyone one id them? Are they just there for the algae?

 

[laverda]

Those are planira in your photos. They are pretty much harmless, but ugly and annoying. They are easy to control using a variety of methods. Many fish will eat them, especially when in the water column. You can blast them off of corals and rocks with a turkey baster or power head. Scooter blennies, target mandarins and many wrasse eat them and are more effective. Also they dissolve very quickly in fresh water. Just swerl any rock or corals around in fresh water for a few seconds and they will come off and dissolve. The fresh dip will kill pods and brittle stars as well so keep them quick. Another method if you have phosphates in your tank is to use Lanthanum chloride. Blue Life sells it as Phosphaye Control. Other companies sell it as well. Dose at half the recommended dosage and over time you will notice the planira slowly disappear. Keep an eye on your phosphates while doing this.. Do not us this method if you do not have phosphates, as it will cause calcium to participate and may suffocate some fish like tangs.
I do not recommend you use flat worm exit, as to many people have killed there tanks using it.

 

[ReeferWarrant]

A wrasse will do a good job at controlling them, my pink streaked wrasse keeps their numbers down. I've used flat worm exit on them before it works but you have to be dilligent and follow the instructions. No deaths occured when I used it, but you have to be aware that those release toxins when they die so if you have a bunch its the toxins in the flatworms not the flatworm exit that kills the tank.