Weird Centipede & Scypha sponge ...SNAIL TOO!

Good day yall! I added new live rock to my tank in January 2009.
1st pic is a sponge (?) Is this a Scypha sponge and if so are they harmful? After 3 years they recently appeared from nowhere, and in many numbers.

2nd pic is of the snail infestation that began several months ago. They are numerous, clearish white (none have patterns, color of any kind with a smooth shell round, ram-horned shape). In a previous post it was suggested to be a worm but clearly you can see, esp by the one Ive pointed out, the shell. When on the glass its easy to see 2 miniscule antenna. Are they ok? Dangerous in high numbers? There are 15-20 on the glass most of the time and 50-100 on the rock at any given time.

3rd & 4th pic and MOST BAFFLING ...this worm/ centipede thing. Approx 1/4 of an inch long, true red at the tip of each end and black in the center. As it slowly slithered along, the tiny legs didnt appear to be moving. Ive only see him once, 3 nights ago. After much searching online, I cant find it. Any ideas what this is, and if so, is it harmful and reproductive?

Please note in my signature that my tank was turned from LS only to Reef in March. Thanks a million if you can help with this!

 

Beat me to the punch........


Best of luck..!!

 

Collonista snails don't seem to do much for keeping the tank clean, but they certainly don't do any harm.

 

WHEW ...I figured these things were all ok ...the bristle worm freaked me out a bit as Ive never seen one ....vibrant red color on his tips. Thanks a billion for your replies ...I appreciate it.

 

This was helpful! I have two worms that look just like your bristle worm...I thought they were bristle worms but wasn't sure. They freaked me out at first!