sand sifter needed - please help!!!

[Jon]

I have a 36 G tank with a crushed coral substrate, about 1 1/2" deep.

Is there some kind of fish or invert that is reef safe that will mix up the substrate and keep it clean.

current livestock:
2 green chromis
2 perc clowns
1 firefish
1 6 line wrasse
2 cleaner shrimp
25+ algae eating snails

I used to have 10 nassarius snails, but the seem to have disappeared as I have not seen any of them for almost a month.