coral banded shrimp and common shrimp

[Int3lSketch]

so i brought a coral banded shrimp and (what i beleive to be) a standard shrimp yesterday from LFS
came home today and both seem to have died, my tank has been running for 5 weeks now
my perameters are all okay, 0 amm 0 nitirite 0nitrate
mg is low at 1200 (waiting on dosing supps) alk at 7.4 dkh 0 phos calc at 440ppm

question is what could have happened to them? all my corals are fine and healthy. the coral band might ave just malted as it seemed the shell was empty, the other shrimp however seemed full if thats the right way to put it.

[Int3lSketch]

should add i used cycled rock and live sand to start the tank. ive been questioning the 0 nitrate for the past 2 weeks, brought new tests ect. even put a raw prawn in and it dissappeared quickly. been feeding my trachy corals raw prawns aswel

[nmotz]

This is the mantis shrimp forum, but I'll try to help anyway :)

Sometimes stuff just dies and there isn't much of a reason why. Your tank is new so it's possible that you still need to build up your tanks biofilter. That means to allow it a bit more time to get bacteria established so it can deal with marine life. Nitrates won't kill shrimp like that unless they are really high.

Or, your shrimp could just be hiding. Molt skins do look like the dead bodies of the shrimps themselves and shrimp normally hide a lot during the day but are active at night.

You can confirm whether they are dead or not by using a flashlight to check out your tank at night.

Hope that helps!