Reef Safe Sand Sifters process the substrate surface, consuming algae, detritus and uneaten food without adversely affecting other organisms in the aquarium.
There are a number of reef safe crabs which do not consume the "good" stuff in your reef tank. Some of the Crabs which sift through and stir the surface of the tank substrate and are considered to be reef safe are:
Here are some great reef safe sand sifting snails which not only consume the detritus and algae on your substrate, but can flip over when they need to, avoiding being eaten or starving.
Many Sea Cucumbers will not only consume detritus and uneaten food, but also snails and other substrate dwelling critters, making them unsuitable for reef aquariums.
These Sea Cucumbers will keep your substrate surface clean as they stir it.
Not all Gobies sift sand. Here are some which do.