Yes it is a Blue Fiji, he gets agolng pretty good with all his other tank mates. I had a 4 stripped that killed another one I had , so I got rid of him.
SO far I havent had any problems with him, And believe me my sand has plenty of life in it. Alot more than 1 horseshoe crab can take care of ...I aslo have 3 olive snails as well there pretty cool Ill take a pic next time I feed them.