This has nothing to do with my 90-gallon tank, but
@TriggerFinger took me on a little walk through memory lane regarding my former mantis shrimp tanks. Actually, I've didn't remember the third one, but I actually had 3. So, this doesn't seem like a normal thing for a lady reefer, but at the time my sons were teenagers, which meant all of their friends were always at my house. Everyone loved the tank, but the mantis shrimp (especially Bo) could draw a crowd.
The first mantis, Princess, was a hitchhiker from the LFS, found in the huge tank of live rock. My son had seen a documentary on mantis shrimp and he was fascinated by them (me too), so we brought Princess home and set up a tank. Princess was probably a common Caribbean mantis shrimp and only got about 2, maybe 2.5 inches long. This picture was from September of 2009, so almost a year after I set up the 46 bowfront. These pictures don't do the colors justice. They are beautiful creatures!
Princess the mantis:
I can't remember how long we had Princess, but at one point, my son talked me into buying Bo, a Gonodactylus smithii mantis (also known as a purple spot mantis). Bo was larger at around 4 inches and I had Bo from late 2009 until sometime in 2012. I guess the biggest downside to owning mantis shrimp (at least to me) was they dined on my CUC. The tanks always had algae because if you put snails in there, they ate them. I know, gross, but not to teenaged boys.
Bo was a smasher (there are also spearers), so he would take those clubbed front appendages and basically beat the tar out of whatever he was trying to get, which was usually a snail. Oddly, Bo's tankmate was a 3-stripe damselfish that was in there for several years with him and eventually went to live in my 46. He never bothered the fish.
I had one unpleasant encounter with Bo when he smashed the crap out of my finger. I usually didn't touch anything in the tank unless I had my tongs in hand (which were hit many times), but I got careless one day and didn't realize he was lurking right at the entrance of his den. I stuck my hand in there to do something quickly and he hit my finger with those smashers...talk about scaring the living crap out me. It also hurt REALLY bad. He hit me more on the nail and it didn't break the skin. Mantis shrimp are also fondly known as "thumb splitters." I guess my experience could have been much worse.

That ended my days of putting anything in the tank without tongs in hand...
Some of the pictures aren't so great, but these show the amazing colors. Note those pink smashing appendages...they hurt...just sayin'
Bo the mantis:
My favorite picture of my son "playing" with Bo. They are supposedly very intelligent (I have no idea who you determine that a mantis shrimp is intelligent), and he would follow you around, probably hoping you stupidly put your hand in the tank to he could smash the daylights out of your finger! ;Hilarious