I had a purple lobster up until 2 days ago. I would have to say they really aren't worth the money. I saw mine very infrequently, and when I did it was only for a few brief seconds. Even at night if I would grab a flashlight and look he was hard to find... Unfortunately something got to him, I'm not sure what would eat it though... any suggestions?
(At least I'm pretty sure it's dead, as I see it's shell floating around the back of the tank and it seems a little thick to just be a molt...)
All in all, go for a flame shrimp (or even better a pair), there much more active and 2 some degree serve a purpose (cleaning, plus food when they spawn). Plus I think there one of the most striking shrimp available. Just my .02 though...