Len's got it right there for ya.
See my avatar? (the picture to the left of this word block, incase youre behind in your terminology)
Electric blue-legged hermit crabs are great cleaners; they both sift some sand, and eat di
atoms and algae off of rocks and sand and such--at least mine have... I would get like 5 of them, just incase. Fancy serpent sea stars are great too; almost too great, I wonder... I had one of my green chromis disappear; dont know if it died, or... 8O Or became a sleeping meal for my star! Anywho, they will eat dead fish, decaying sponges, and other forms of nasty detritus and garbage. Definitely get at least two; maybe a red one and a tiger-banded or blue...?
Snails; gotta love em! I have a super tongan nassarius snail thats the fastest snail youll ever see! Fun to watch,
and eats algae and stuff! You cant go wrong with at least one of them... You also cant go wrong with Margaritas; those guys I practically set down running when placing them in the tank after acclimation! They started eating right as I set them down! defnitely go with at least 10-15 of them.
If you want to get a bit more diverse and colorful in your cleanup crew, a Fancy Turban snail is an awesome, spectacular addition to the janitorial work force! Just one should do, though you can always do more.
Finally, you gotta toss in the shrimp! My scarlet skunk cleaner shrimp eats just about everything in that tank, from decaying food and stuff, to dead skin on my fingers! Plus, they are just too cool to watch; great behaviors and colors!
Well, that about does it, as far as I know; somebody slap me if Ive forgotten anything!
Hope that helps! 8)