Trichormus variabilis is a filamentous cyanobacterium found in freshwater environments. It forms long, unbranched filaments composed of cylindrical cells enclosed in a gelatinous sheath. Each cell is about 5-10 micrometers wide and connected end to end. The organism is pigmented with chlorophyll a and phycobiliproteins, giving it a blue-green to green color. Reproduction occurs through filament fragmentation, and it thrives in ponds, lakes, and slow-moving streams, contributing to nutrient cycling in aquatic ecosystems.