Hoverfish

The Hoverfish are -like beings, but floating not in water but in the air. They are intelligent enough to obey commands, but do not seem to like humans. A group of ten Hoverfish are held by Mom and her sons.

Production
The Hoverfish were originally seen in the storyboard of the episode "Overclockwise". It was not entirely clear in the storyboard if they were biological or mechanical (robotic) creatures, but it was made clear in the actual episode that they're robots.

The commentary for "Overclockwise" revealed that the hoverfish that tells Bender to return to Mom is actually voiced by both Phil LaMarr and John DiMaggio simultaneously.

Additional information
They could be inspired by sentinels of Matrix series.