Radioplankton are tiny, free-floating, carbon-based algae that inhabit a sub-category of Gas Giant planets called Gas Giants with Water-Based Life. Unlike some other alien species, Radioplankton cannot be directly observed, and are only known to exist through the text descriptions on System Maps.
Gas giant with water-based life. This is primarily a hydrogen and helium based atmospheric gas giant, but not far below the surface exists life based in the water-cloud layer just below the atmospheric surface. The chemistry of this gaseous region is far from equilibrium, with a surprising excess of oxygen and many carbon-based compounds giving it some vivid colors. As with many such gaseous living systems, it is underpinned by vast quantities of free-floating radioplankton - tiny carbon-based algae, each retaining a small quantity of liquid water, extracting their energy from intense radiation flux.
Some Gas Giants with Water-Based Life that support Radioplankton are listed below.