Spirodela Polyrrhiza - Tissue Culture - Tropica

Spirodela polyrrhiza | Greater Duckweed, a Fast-Growing Floating Plant for Shade and Cover

Spirodela polyrrhiza, commonly known as Greater Duckweed, is a floating plant with small, round, green fronds and short roots that hang down into the water. It is larger than common duckweed, and it spreads across the surface to give a calm, pond-like look. Beyond appearance, it is a practical plant: the cover it creates gives fish and shrimp shelter, softens bright lighting, and helps keep a tank balanced.

Easy to care for and fast growing, it suits beginners and experienced aquarists alike. It is especially useful in tanks with fish that prefer dim, shaded water, in breeding setups where fry need cover, and in planted tanks where excess nutrients need soaking up.

Key Benefits

• Natural shade: Offers shelter for fish and reduces light penetration, which suits shy and blackwater species
• Algae control: Competes with algae for nutrients, helping to limit algae growth
• Water quality: Absorbs excess nutrients efficiently as it grows
• Cover for fry and shrimp: The roots and surface mat give young fish and shrimplets a sheltered place to hide

Care at a Glance

• Scientific name: Spirodela polyrrhiza
• Also known as: Greater Duckweed, Giant Duckweed
• Origin: North America
• Type: Floating plant
• Growth rate: Fast
• Light demand: Low to moderate
• CO2: Not required
• Best placement: Floating on the water surface

Keeping It Balanced

Because Spirodela grows rapidly, regular thinning is recommended. Left unchecked, it can cover the whole surface and block light from submerged plants, so scoop out the excess every week or two to keep the coverage balanced. The surface should stay partly open so that light reaches your submerged plants and so that fish can reach the surface to breathe. If you ever need to remove it entirely, be aware that duckweed is hard to eliminate once established, so start with a small amount.

Getting Started

Simply place the plants on the water surface. They need no planting or attachment. For best growth, keep the light low to moderate and make sure the tank has a supply of nutrients. Floating plants grow most vigorously in calm water, so a gentle flow at the surface suits them best.

Compatible With

• All community fish, shrimp, and snails
• Especially suited to fish that appreciate shade and surface cover, such as bettas, gouramis, and many blackwater species
• Excellent in breeding and shrimp tanks for the shelter it offers to fry and shrimplets
• Useful in planted and low-tech tanks as a nutrient sponge to help keep water clear