Amazon Sword vs Common Duckweed

They do not overlap much in exact placement, which is why this comparison is more about adjacent options than true one-for-one replacements.

Amazon Sword is a rosette / crown plant that usually reaches about 50 cm tall by 40 cm wide. Common Duckweed is a floating plant that usually reaches about 0.2 cm tall by 1 cm wide.

Their benefit profile differs enough that the better choice depends more heavily on what the rest of the tank needs.

The comparison is still useful because it shows whether you are choosing between two similar plants or two plants that only look related at first glance.

Choose Amazon Sword when its exact growth habit fits the open space you have and you want the finished scape to lean toward its shape, texture, or spread.

Amazon Sword gives you more propagation flexibility through adventitious plantlets and side shoots / offsets.

Amazon Sword also suits keepers who want moderate light and no added CO2, with moderate growth, low maintenance, and beginner difficulty.

Choose Common Duckweed when its shape, mature size, or planting style gives the scape a cleaner finish than forcing Amazon Sword into the same role.

Common Duckweed makes more sense in lower-light scapes.

Common Duckweed is the tidier fit when space is limited.

Common Duckweed gives denser visual cover when fish security matters more.

Common Duckweed fits a routine built around low light and no added CO2, with fast growth, high maintenance, and beginner difficulty.

Role overlap lands at 0/100 and care similarity lands at 68/100. Treat those numbers as a shortcut for the decision, not as a replacement for looking at mature size and placement.

Amazon Sword is rooted in substrate with nutrient-rich substrate preferred and feeds mainly as a root feeder. Common Duckweed is free-floating with no substrate required and feeds mainly as a water column feeder.

Their mature height diverges enough that they stop being true one-for-one replacements.

If the tank already has several demanding plants, the easier choice is the one that matches your existing light, CO2, and trimming routine.

If you need a true substitute, keep looking. This pair is more useful as a contrast because the plants ask for different layout decisions once they mature.

A practical way to decide is to imagine the tank six months from now. The better plant is the one that still fits the same space after several trims, not the one that only looks right on planting day.

Amazon Sword and Common Duckweed look like a comparison pair on the surface, but they usually serve different jobs in a planted tank. The smarter decision is to start from the layout problem you are solving, then choose the plant that belongs in that role instead of comparing them as direct substitutes.