Anyone know what this is?

[mikeysorrell]

This came with some live rock.



It has grown into this:





I would be very interested to find out what it is and what it may eventually turn into, hopefully nothing nasty.

I am a newbie marine aquarist and therefore new to identifying marine invertebrates. All types of creatures seem to be crawling out of the "stonework" as it were, including a small, odd looking slug like animal with little spines. Also there appears to be a myriad of tiny, almost microscopic white creatures all over the glass of the tank, should I be worried, I don't want them to overrun the tank.

Any help would be very gratefully received.

Thanks,
Michael

 

[kdpuffer]

Well the thing in the pics looks like a snake zoa to me. Mine started as little nobs like that but have grown and turned green and open up at night. Either that or tube sponge, either way they are harmless. The tiny white bugs are copepods, they are also harmless and help eat debris in the tank. They are also what mandarin dragonets eat. Now the spiky slug, that sounds like a nudibranch which is typically bad. They will only eat one thing and one thing only and once that food is gone they die and often can cause problems. The real kicker is that they tend to eat coral!!!!!!

 

[mikeysorrell]

Thank you very much for your help. I look forward to the tube opening up.
I have been investigating the slug like creature on the internet and watching it moving, and I think that it is a stomatella snail. There are several smaller examples now appearing around the tank, taking care of the ever growing various forms of algae.
I have to say that marine aquariums are completely fascinating, I can spend hours just sitting in front of the tank, finding new things all the time.
Michael