What is going on here ??

[Snappy]

Hermit crabs, shrimp & some other inverts molt when their body outgrows it's present outer shell. The white critters are likely "pods", copepods, amphiphods, mysis shrimp, ect. That is a good sign that your tank is probably healthy. They are beneficial and something you want to have in your tank. Over the next several months you will see all kinds of things growing in the tank, bristle worms, feather dusters, peanut worms, ect. Take a flashlight and check it out after the lights have been out for a few hours and you will see a whole other world. Welcome to reef keeping.

[skylord]

You may want to add a few shells so that when the crab molts and outgrows its current home he has something to move into.

[NateL]

+1 on the molt, no worries happens all the time, but it still can throw you for a loop.

[Sam1969]

I have Plenty of empty shells in the tank of various sizes, for them to move into. However this still stumps me where the second blue legged shrimp came from ?? that certain is good news about the worms though, I was beginning to worry...

thanks for the replies

[Rippin]

Originally Posted by Sam1969

I have Plenty of empty shells in the tank of various sizes, for them to move into. However this still stumps me where the second blue legged shrimp came from ?? that certain is good news about the worms though, I was beginning to worry...

thanks for the replies

I don't think you understood some of the replies. You most probably don't have two blue-legged crabs. The one that you thought was "dead" is most probably the discarded, molted shell of the original crab. It is possible though, that the live rock that you bought/received did have a hitch hicker crab in it.