I'm still examining my photos of the holdfast critters and trying to identify what I've found. I'll post what I have tomorrow, identified or not.
In the meantime, isn't this the cutest starfish ever?
It's on a piece of dead eelgrass and a bit of kelp. And it's under 1/4 inch point to point.
It isn't from the holdfast; I have a spare water container, for filtering used water through sand and airing it. I add green stuff from time to time, for the clorophyll; when it dies, I take it out and dump it on my compost. Luckily, I checked it first. I don't know how this starfish got there.
It's very much alive; while I watched, it crawled off the eelgrass onto the kelp. And now it's in the main tank, hidden in the sea lettuce.