Can Giant Duckweed and Hornwort Grow Together?

Giant Duckweed and Hornwort share a workable water window around 15 to 30 °C, pH 6 to 8, and 2 to 15 dGH.

Both plants are comfortable in freshwater, so salinity is not a meaningful obstacle.

Both prefer gentle, low-flow water, so circulation can be planned as one steady pattern.

Both fit low light and no added CO2, so one lighting and CO2 plan can support the pair.

Both plants naturally lean toward the floating, which is why spacing, pruning, and final mature size matter more than they do in a more staggered planting mix.

Giant Duckweed reaches about 3 cm tall by 1 cm wide, while Hornwort reaches about 100 cm tall by 15 cm wide. Use those mature sizes for the layout, not the small nursery portions you bring home.

Shade is not the main concern here, which makes the layout easier to keep balanced over time.

Both are typically free-floating with no substrate required and feed mainly as water column feeders. The method is simple, but it also means the same planting zone can feel crowded if they are placed too close together.

They can share the space, but the scape will stay cleaner if you leave more room than the labels alone might suggest.

Giant Duckweed brings fast growth, high maintenance, and beginner difficulty. Hornwort brings fast growth, moderate maintenance, and beginner difficulty. If one grows much faster, trim that plant before it starts making the other look like the problem.

The practical watch-outs are that both plants tend to work in the floating, so spacing matters more than usual; and that you will want to leave more room than usual for mature spread and routine thinning; and that growth pace and maintenance rhythm are uneven, so the stronger grower can dominate if pruning slips.

The strongest reasons to try the mix are that they share a workable temperature window around 15 to 30 °C; and that their flow preferences sit close enough to tune one layout around both plants.

Use this pairing when you want two plants that can share one routine without forcing a compromise at every step. It is strongest in tanks where mature spacing is planned before the plants fill in.

The simple success test is whether both plants still look healthy after the faster grower has been trimmed several times. If one keeps declining after routine care, the layout is probably asking too much of it.