Common Duckweed vs Pinnatifida

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

Common Duckweed is a floating plant that usually reaches about 0.2 cm tall by 1 cm wide. Pinnatifida is a stem plant that usually reaches about 40 cm tall by 20 cm wide.

They also share practical benefits such as grazing surfaces and shrimp refuge, so the decision is not only about looks.

The strongest overlap signals are practical: they offer many of the same practical benefits, including good grazing surface and good refuge for shrimp.

Choose Common Duckweed 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.

Common Duckweed is the easier keep when you want the simpler option.

Common Duckweed makes more sense in lower-light scapes.

Common Duckweed is the tidier fit when space is limited.

Common Duckweed also suits keepers who want low light and no added CO2, with fast growth, high maintenance, and beginner difficulty.

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

Pinnatifida gives you more propagation flexibility through stem cuttings and side shoots / offsets and runners / stolons.

Pinnatifida fits a routine built around moderate light and recommended added CO2, with moderate growth, moderate maintenance, and intermediate difficulty.

Role overlap lands at 12/100 and care similarity lands at 76/100. Treat those numbers as a shortcut for the decision, not as a replacement for looking at mature size and placement.

Common Duckweed is free-floating with no substrate required and feeds mainly as a water column feeder. Pinnatifida is attached / wedged to hardscape with no substrate required and feeds mainly as a mixed 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.

Common Duckweed and Pinnatifida 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.