Found this in my tank today

[Vinh]

Can anyone identify what this is?

 

[cloak]

Nudibranch of some sort. In most cases these are bad, so you might want to remove it just to be safe. Also, usually when there's one there's more, so definitely keep your eyes peeled. GL.

http://www.lionfishlair.com/hitchhiker/nudibranchzoa.shtml

 

[Triggreef]

Looks like a zoa eating nudi. Do you have a lot of zoas? They often come on those big wild colonies some stores bring in. They sell them cheap and that's what happens.

You should experiment with what is effective in killing it, so you know what and how long to use whatever you find that works. Assuming you may need to test your tank. I find flatworm exit works better to kill these guys than Bayer. Peroxide might even work better than both of those.

 

[Sabellafella]

^^^ 100%

 

[cloak]

Before you go adding chemicals to the tank you might want to build yourself a siphon like the one pictured in the link below and see if you can manually remove these things first. I know it can be a little tedious, but this is how I got rid of mine. GL.

http://www.melevsreef.com/flatworms.html

 

[Vinh]

I bought some zoas a few weeks ago. So far I've been able to rid of 2. Thankfully they're easy to catch when you see them.