I'm not sure if this is the right place to post this so sorry in advanced. I am having trouble trying to identify these little tentacle like things. I noticed a couple on a piece of live rock when I first started my tank in September. But now they're everywhere! When they're not extend they look like little cactuses and when they extend they're about an 1" to 2". If you need more photos I can try, but it's really hard trying to focus on them.