Can i put a spearer in there?

I use to have 2 Peacock mantis shrimps but the one in my 6 gallon eclipse tank died. It jumped out when i was takeing the top off to clean it he went about 2 feet into the air trying to hit me but didint it landed into a bucket full of live silverslides and ghost shrimp that i feed it and it went crazy i got him in a net and put it back in the tank it died within an hour probally because it was very hurt from the fall. Well back to the point of this post, Can i put a spearer in my 6 gallon eclipse tank with 2-3 inches of crushed coral and a good size pice of live rock. I know spearers need sand and need bigger tanks than smashers thats why i asked this.
It depends on the species of spearer. Some such as Pullosquilla are only 17 mm long and I keep them in cups of sand with a only an inch or two of seawater. If you mean Pseudosquilla, no problem. You might add some sand gradually to the crushed coral, but it should be fine. If you mean a squillid or Lysiosquillid, it is not a good idea.