[bluespotjawfish]

I've seen tentacles extend more in low light conditions as well. And, if they are frequently disturbed by fish (either by swimming across them or picking at them), they also stay as tight as possible to protect themselves.

Here are some pics of mine. I have 13 different varieties, 11 of which are pictured. The zoo rocks in the second and last photo were completely eaten down to bare rock by my Emporer Angel. Once the angel was removed they came back in full force!