Floating Salvinia plant for fish tanks. Note// Salvinia plant is completely and fundamentally different from duckweed. It differs in shape, color, and appearance. Salvinia plant comes in the form of a tangled, net-like floating mass. As for duckweed, it comes in the form of independent granules. Salvinia minima - Small Salvinia plant Salvinia molesta - Giant Salvinia plant Easy to care for floating plant. Does not require CO2.