What is this and should I be worried

[abirozy]

Hello

I am relatively new to the hobby and have a JBJ 28 gallon nano. I have recently noticed something popping up near my vargus cespitularia...It is very small, clear and has a round ball at the end of the strand. At first I thought it was just strands of slime from a new coral that had caught on a rock, but I scrubbed the rock with a toothbrush and it came back.

For reference on size, the stalk of the vargus it is near is only about 1/4 - 1/2 in diameter.

Sorry, pic is turned sideways. Could not figure out how to rotate it.

 

[johnanddawn]

It's really hard to see with that pic, but I almost see a mouth in the middle and the "strands with the bubble"you describe are the tentacles of an aptasia
It looks like its stalk is completely sucked into a hole and is just poking its head out

 

[Reefing Madness]

Strawberry Anemone or Ball Anemone

 

[Wbrian]

If you're talking about all that stringy looking stuff, looks like some type of algae to me...