Sliver-Slurper

Silver Slurpers are a race of thin, tall, greenish aliens that feed on waste and sewage left by other races. They possess no arms, have large eyes on the top of their head, and their feet hold suction cups to feed on said materials. After feeding, a Silver Slurper can grow to colossal sizes, rounding out like a hot air balloon. They aren't aggressive towards other alien races, yet gives off a foul-smelling odor. Despite their huge size after eating, they don't show any signs of strain.

Technology
Silver Slurpers have full control over gravitational functions: able to simply "float" after feasting on sewage and waste to return to their spaceship. The spaceships have huge strange areas for food, much like giant tankers.