What is it? you said long tentacle is it a condy? My condy will be so big and have a long stalk and take up the space of a small plate, long whitish tentacle and purple tips, then in the morning sometimes I can't even hardly find it, it shrinks up turns orange and looks like a silver dollar size blob of orange jello, sometimes with dark purple strings hanging out it. Sometimes I think it's the most entertaining thing in my tank and I love to feed it and watch it pull food to it's mouth,(feed only when tentacle are out) I have no idea how that thing gets so big and so small but it is healthy and normal. sorry if this is a little long but if that's what you have it's normal IMO.