Today I get the feeling that this "thing" is alive so it's become more urgent for me to find out what it is so I will know what to do for it, if anything. The reason I now think it's alive is because it changed..... when I got up this morning and turned on the aquarium lights, it was very shriveled/skinny looking, where as before it looked full and plump. I don't know if it's starving to death or if it plumps up once the lights are on but it has definitely changed. If it's a living thing that I need to care for, I better figure it out fast. There's not that much info out there on sea squirts and tunicates, at least not in my searches yet.
Sue