ok my old(first saltwater set up in a 10gal) was like this...invert tank star fish, hermit crabs, cleaner crabs, a decoy scorpion,and some anenomes...with live rock only not live sand...ran a basic penguin 125 filter with a home made double strip light one that was 10,000K and a Antic Blue cheap easy to maintain and was cool to watch all the inverts and to feed the anenomes and decoc scorpion...thats just my opinion and i have been atoying with seting this idea up again for the past couple of weeks(haha that why i just popped up out of nowhere into the SW thread...plus i live in hawaii its almost mandatory that if your into fish tanks you need a SW one...) Good luck any who on your decision.
P.S. dont do a mantis...they have the potential to shatter a tank...really big mess to clean up, they are cool to watch but not when they have the striking power compared to that of a small caliber bullet...dangerous for tank and to clean the tank...just my opinion