What is this? Should I be worried?

[ReefGrrl]

Thanks for that idea - so I looked at photos of sea cucumbers in various growth phases and I don't think so. It was about 5mm across, so fairly large as compared to some critters. The pink-coloured body was about 3mm and appeared to have a white dot in the centre and was kind of dome-shaped.

My first impression when I first spotted it was that the head of a bristleworm had grabbed a piece of seaweed and crawled somehow up the glass - that's the colour pink it was. Then when I looked closer I saw it had these knobbly white legs.

I'm not sure whether I hope it appears again or not. Maybe it got sucked into the pump.