Ahh, you're looking for sand sifters? I'm guessing its not a planted tank then. I find that planted tanks are great for aerating sand.
Lessee.
Yeah, loaches will eat most inverts. That leaves out most shrimp and snails. Oh, and
btw, loaches are VERY social creatures; one will be most unhappy. We recommend a minimum of 3, although of course more is better. Do know clowns will top out at about 12 inches long when well kept.
I'm hesitant to suggest the blue lobster (aka a type of crayfish). They can be dangerous to your fish, especially at night when the fish are sleeping and the crayfish is wide awake. Some folks have had good success with them, others have lost fish to em.
There are some fish which are sand sifting (the SA geophagus group for example). Thing is, even with a 55g you have fish which will get big and aggressive. Severums top out 6-8 inches and are semi aggressive, Black Ghost Knifes top out around 20 inches or so and will eat any fish they get into their mouths, the clown loach as I said before can reach a foot in length, and the needlefish will likely make them all look tiny, as they can reach well over 2 feet long in the wild and will also hunt any fish smaller then them. I'm not sure exactly how big blood parrotfish get, but they too are not small fish.
You may want to look into sifting the sand yourself; a chopstick or a clean "fro" pick will work fine.