what are they?

[Maddoggvup]

these little green things just pop up out of nowhere. they're green and have little fingers. sorry best pic I can take. what are they?

 

[Maddoggvup]

after a closer look. it looks like fluorescent green feather dusters...?

 

[Maddoggvup]

or fluorescent green tube worms...?

 

[saltyfilmfolks]

Those would be a type of colonial hydroid.
Putty and super glue.

 

[Maddoggvup]

I have seen some post that they are bad. why?

 

[Maddoggvup]

what is the difference between tubeworms, feather duster and hydroids?

 

[saltyfilmfolks]

They sting , both corals and fish if they come in contact. They also spread and these burrow into the rock like you see there.

 

[saltyfilmfolks]

what is the difference between tubeworms, feather duster and hydroids?

Feather dusters are tube worms. Just with different feeding strategies. Hydroids are similar but more closely related to jellyfish than worms.

 

[Maddoggvup]

best way of telling the difference?

 

[saltyfilmfolks]

Research. Mainly and experience.

 

[Maddoggvup]

thank you. You have been a lot of help on this question and many others.

 

[saltyfilmfolks]

Your welcome. I like reefs. And bugs

This guy is amazing. Hours of reading on micro fauna and biology.
http://www.ronshimek.com/worms.html

 

[jsh mee]

Get rid of them while you can. They can be very invasive. Those little guys are one thing that I thought was pretty at first and never bothered to deal with. Now it would be nearly impossible for me to get rid of them.

They have never harmed much of anything in my experience, but they do restrict growth of zoas and encrusting corals. It's super annoying having to get in there with tweezers all the time yanking them out where I don't want them.