Personally I wouldn't. Dragonettes can get aggressive when mixing species. Also you have a fat one, congrats ,I've seen way too many skinny ones!!! Adding another may diminish your pod population alot faster and not be able to support two unless you have a large tank with lots of live rock.
Beauty is in the eye of the beholder. Whilst I personally think Aiptasia and Manjanos are pests, we have people who buy them where I work because they like them. :)
If you do want to get rid, lemon juice and Kalkwasser works. Just mix it up and syringe a little bit into the mouth of each one.
I know you've already got the tang now, but just to add, I kept a yellow tang with a mandarin and corals with absolutely no problems. The only time I had issues was she started to outgrow my 60gal and became a bit aggressive to all tankmates, especially my yellow striped maroon clown. Since...
Mine are all soft corals such as mushrooms, xenia, toadstool, etc. Most of my hard corals died before I even got the puffer which is why I risked it. :)
Mine is the Diodon holocanthus. And he's an absolute cutie!!
I've only had experience with the fuzzy (still do:)). Mine is kept in a reef tank complete with shrimp, crabs and snails with absolutely no problems whatsoever. It can be a bit tricky getting some of them to eat, but mine is now one of the first fish to go for the food.
Everything Ace said!
But
I have a porcupine puffer in my reef tank with hermits and snails and a pistol shrimp. He's been in there quite a few months now and absolutely no trouble.
I do tend to push the rules and what i put in my tank I don't necessarily advise to others:)
They sound like pineapple sponges to me - harmless. I have loads of them but there are pictures in this link that may help you with an I.D
Ps amended the title for you;)
Whilst they are known to secrete a toxin, I've had 2 that never did, even when they were dying. (first one was when I was a newbie and given VERY bad adc=vice and wasn't up on water levels!!! The second was a lot more recent and got zapped by a Mantis Shrimp!!!
We get them in at the LFS where...
You may not find him under Blennies!!! They're also known as engineer gobies, but they're neither a blenny or a goby!!!!
Latin name is Pholidichthys leucotaenia. They do better in groups but this came in as a return from a customer who was shutting down his tank. If I come across any more that...