I thought it was when you poop and theres nothing in the toilet. Oh wait nevermind thats the ghost cigar fish. Very common in the trade but i believe they are a brackish water species. Disappearus Fecesius is the scientific name.
They could be ghost. I have read of some living in salt water. I don't know for how long though. The person said they throw them in their salt tank to be food and that they see them weeks later.
NO This is not the feeder ghost shrimp This is a anemone/commence ghost shrimp clear with white spot and a black and orange tail the pet shop just called it a ghost shrimp i don't know if that is official or anything I try and find a picture
I've never seen one for sale either, so that's a great addition to your tank. I'd assume he's like most other shrimp, and will appreciate a little bit of meaty food from your feeding tongs now and then.