Common Duckweed vs River Buttercup

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. River Buttercup is a stolon / runner plant that usually reaches about 15 cm tall by 20 cm wide.

They also share practical benefits such as fry refuge, 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 refuge for fry and 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 River Buttercup when its shape, mature size, or planting style gives the scape a cleaner finish than forcing Common Duckweed into the same role.

River Buttercup is the better pick when you prefer its exact shape and placement style.

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

Role overlap lands at 12/100 and care similarity lands at 64/100. 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. River Buttercup is rooted in substrate with nutrient-rich substrate preferred and feeds mainly as a mixed feeder.

Lighting expectations are different enough that they do not drop into the same setup equally well.

Also watch that one of them casts noticeably more shade, so the effect on the tank feels different.

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 River Buttercup 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.