Sea apple?

[sid2003]

My girlfriend has a small creature in her 10 gallon tank that when you turn the lights off it will grow a christmas tree looking appendage for a little while, then it goes back in after a while. It's really weird. Is this a sea apple? If not what could it be?

 

[kreach]

It could be a sea apple or another type of sea cucumber, but a much better description or pic is necessary to be sure...

 

[black99l]

if it is a sea apple pray that it doesn't die. from what i hear when dieing they will release enough poisons to completely wipe out a decent sized tank.
T