What is this?

[TheBear78]

Good afternoon.
I was walking round a LFS this past weekend and came across these. I couldn't see a sign saying what they were and I couldn't see anyone to ask.
Any ideas?

 

[Jekyl]

Sea apple / cucumber

 

[Eagle_Steve]

Good afternoon.
I was walking round a LFS this past weekend and came across these. I couldn't see a sign saying what they were and I couldn't see anyone to ask.
Any ideas?

It is a sea apple.

Sea apple - Wikipedia

en.wikipedia.org

 

[davidcalgary29]

...otherwise known as a toxic bomb waiting to explode in your tank! Not for the timid, unprepared, and/or unlucky novice.

 

[TheBear78]

Thank you.
Looks very interesting but I guess that is the trap!

 

[davidcalgary29]

Well, it looks like a pineapple grenade for a reason. I'd maybe risk one in a species tank with excellent filtration, a reactor running carbon, no sharp or pointy things, and only rehomed clownfish, which are known biters, to reduce sadness in the event of a tank wipeout.