I did a thread asking if anybody could give me an ID or even send me in the direction of somebody who might know. I talked to 2 professors (marine biologists) at 2 different universities. I asked the 2 that I know personally who work at the Bailey Matthews National Shell Museum. I even asked at Wet Web Media. No good answers. One wanted me to cut it open to see what it looked like inside! No way! And I only assume it's a algae. Many people think it's a sponge, but it has no incurrent pores and no excurrent holes for intake and discharge of water like every other sponge.
Yes, it's still alive. I had it in quarantine for a month, then in my sump for a few weeks and it's been in my DT since I did the new rockscape a week ago. It has gone through a couple of changes. When I got it home it had the 'spikes' sticking out. After 2 weeks tiny round balls developed at the ends of the spikes. A week later the tiny balls (still very small) developed spikes just like the big ball. Two weeks later the spikes on the big ball started to shrink and most of the small balls came off. I assume that is it's reproduction cycle, but I really don't know for sure. I did find a few of the small balls in the quarantine tank.
This photo is after the spikes became short and the small spike balls started to come off.
20180815_121922_001 by
Ron Lindensmith, on Flickr