hitchhiker id

I've came across 3 of these so far in my aquarium. Just wondering if anyone can identify these and let me know if they're good or bad. They are about 0.75 centimeters long. Thanks in advance.

Hey everyone, I got a hitchhiker today. Not sure if he's reef safe or not? He's tiny at the moment. Any help would be greatly appreciated. Thanks

Hi All, We're in the process of moving all our corals from our nano to 100g (no live rock), while checking/cleaning our one of our corals it accidentally broke where the skeleton had died (we've been nursing it back to health) in doing so it revealed the frag plug below which low and behold had...

Hello! I added 6 Zoa frags yesterday and dipped them all in "The Dip" from Fauna Marin before putting them in my tank. I noticed something on one frag, I think it's some kind of sponge? Today, all, except the frag with the "sponge" are partly or even fully open. Can someone tell me if it is...

I was looking in my tank the other night about 30 mins after daylight switched to moonlight. Worm was about 0.5" in length and transparent. I'm afraid it could be a young bobbit or some other predatory worm. After some initial googling it kind of looks like a Dorvilleidae worm also. I really...

Found this blob on my rock last night. In the pic it almost looks like a star shape. Moves very slowly. Initially thought it was part of the super glue used to secure rocks. Anybody have thoughts on an ID?