Never seen anything like this before.. Ive been watching this thing grow now for a couple months... At first when is was very small I thought it was a ricordea.. But, I am starting to think differently now!
Pictures are under LED's i'll try and get something more clear-- was using my phone!
I had some of these pop up in my aquarium. Mine turned out to be plate corals. If you can touch the tentacles and they shrivel up revealing a hard skeleton, I'll bet they are plates. Mine were amber gel with neon green tentacles.