Six-Line Wrasse Dead This Morning

[chpolack]

I purchased a six-line wrasse two days ago and introduced it into my tank. However, when I woke up this morning, I couldn't find it anywhere. Finally, upon closer inspection, I found it on the sand at the bottom of my tank with its tail missing. I'm not sure how it could've died, but it seemed fine yesterday. I'm not sure if maybe I didn't acclimate him correctly, but I used the same method for my fish that have been in my tank for a couple weeks. I don't think I have any other aggressive fish or inverts in my tank:
------14G Biocube---- (Established on 12/17/2010)

Fish

• 
  Clownfish
• 
  Firefish
• 
  Purple Firefish
  
  Invertebrates
  • 
    Serpent Star
    Pincushion Urchin
  Corals (all about an inch large)

• 
  Ricordia
  Candy Cane
  2 Polyps (purple green & purple/pink)

I also have a few hermit crabs and snails.
If there is any more information you need please let me know.

 

[chpolack]

More news:
I think I have found pieces of the fish's tail scattered across the sand in the tank. There appear to be about 15 small blue/green fragments on the sand. I'm not sure if this is from something else, or if this could somehow help in the investigation.

 

[btldreef]

That's a lot to have in a tank that's only been up for a month.
What are you water readings?

 

[chpolack]

Water Conditions
pH: 8.2
kH: 179 ppm
Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate: Less than 10, more than 5