not going to lie your post was interestingly formal. impressive
good idea with the silk, it looks realistic
since it's 15 gallons you might want to look at schooling fish or small, attractive fish such as neon tetras (or all the other tetras), guppies, mollies, platies etc. with these you could still have the crustaceans, some shrimp would be quite cute. crabs are cute as anything and fun to watch, but need lots of easy access to oxygen so maybe not the best of ideas.
personally im a cichlid person, so i'd be looking at kribs or shellies and some dither fish... but thats me!
hope you find something you like! why not visit the lfs
and see what catches your eye?