Guppy grass (picture source) is a light to dark green stem plant. They are slender, fully aquatic plants. Their stems reach a length of 20 inches and are heavily branched with fine shoots. The lower nodes often have a weakly developed, white root system.
Guppy grass plants are covered in very fine needle-like leaves of about an inch in length. The leaves are whorled around the stem and show some variation depending on whether the plant is grown rooted or kept as a floating plant.