Duckweed

Duckweed is rated as a medium-light plant. Medium light is roughly what a mid-range planted-tank LED delivers over a standard-depth tank; going brighter without more CO2 and fertilizer usually shows up as algae rather than faster growth. CO2 is not needed for it, and its care difficulty is listed as beginner.

No. Duckweed does not need injected CO2, so it suits low-tech tanks without a CO2 system. It is a medium-light plant. For nutrients: tolerates inert substrate with occasional root tabs. Keep light, CO2 and fertilizer in balance, because raising one without the others is the most common cause of algae in planted tanks.

Splits via runners. Thin colony every 2-3 weeks during peak growth. Let each new plantlet grow its own roots and a few leaves before cutting the runner, then replant it at the same depth as the parent. New growth comes in fastest when the tank matches its needs: medium light, with CO2 not needed.

Yes. Duckweed is listed at beginner difficulty. It needs medium light, CO2 is not needed, and for nutrients: tolerates inert substrate with occasional root tabs. Stable light, nutrients and water changes matter more than any single product. Check these needs against your current setup before buying.