Can Dwarf Hairgrass and Large Ammannia Grow Together?

Dwarf Hairgrass and Large Ammannia share a workable water window around 22 to 28 °C, pH 6 to 7.5, and 4 to 12 dGH.

Dwarf Hairgrass is listed for freshwater to lightly brackish water, while Large Ammannia is listed for freshwater. Keep the tank in the shared part of those tolerances rather than pushing either plant to an edge.

Both prefer moderate flow, so circulation can be planned as one steady pattern.

Their light and CO2 needs are close enough for one routine: Dwarf Hairgrass does best with moderate light and recommended added CO2, while Large Ammannia does best with high light and recommended added CO2.

They naturally settle into different parts of the scape, which gives you more room to use each species for what it does best instead of forcing direct competition.

Dwarf Hairgrass reaches about 7 cm tall by 15 cm wide, while Large Ammannia reaches about 50 cm tall by 15 cm wide. Use those mature sizes for the layout, not the small nursery portions you bring home.

Shade is the biggest layout risk. If the taller or denser plant gets ahead, the other one can slowly decline even when water and nutrients still look fine.

Dwarf Hairgrass is typically rooted in substrate with nutrient-rich substrate preferred and feeds mainly as a root feeder. Large Ammannia is typically rooted in substrate with nutrient-rich substrate preferred and feeds mainly as a mixed feeder. That difference can make the pairing easier to arrange than two plants fighting for the exact same root or attachment zone.

Mature size is not the main thing working against this pairing, so normal maintenance is usually enough to keep the scape readable.

Dwarf Hairgrass brings moderate growth, moderate maintenance, and intermediate difficulty. Large Ammannia brings moderate growth, high maintenance, and advanced difficulty. If one grows much faster, trim that plant before it starts making the other look like the problem.

The main watch-out is that shade becomes a real risk here, especially once the taller or broader plant settles in.

The strongest reasons to try the mix are that they share a workable temperature window around 22 to 28 °C; and that their flow preferences sit close enough to tune one layout around both plants.

Use this pairing when you are willing to manage the scape, not when you want a plant-and-forget combination. Start with more spacing than you think you need, then adjust once both plants show their real growth pace.

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.