I am happiest with a pair of long tweezers in hand. There is a very specific rhythm to planting a new tank. You separate the tissue culture, grip a tiny plug of dwarf hairgrass by the roots, and push it deep into the dark aquasoil. You repeat this fifty times. You step back, admire the neat little rows, and wait for a green carpet to fill in.
One week later, the grass turns brown and looks dead.
If you’re a beginner in planted tanks, this is when the panic might start to set in. You may start thinking you got a bad batch or that maybe your lighting is off. What you are seeing is totally normal, and it’s a phase called melting. Almost every aquascaper goes through this phase with dwarf hairgrass (Eleocharis parvula or Eleocharis acicularis).
Seeing a crypt finally take a liking to your tank is strangely satisfying, and hairgrass takes that same patience. Understanding the melt and providing the proper conditions for the plant to recover is really the key.
The Science of the Melt
The majority of commercial aquatic plant nurseries cultivate their stock emersed. This involves growing the plants out of the water in extremely humid conditions. This method of plant cultivation avoids algae outbreaks in the nursery and accelerates growth since the leaves are exposed to atmospheric carbon dioxide.
When you bring dwarf hairgrass home and put it in your aquarium, the plant undergoes a shock. The nursery’s terrestrial leaves that grew on it are not made to do gas exchanges underwater. To cope, the plant drops those old leaves.
Once the blades turn brown, they mush and eventually fall off. The plant is diverting all of its energy down into its root system in order to push out new, submerged-grown needles that will actually be able to function in an aquatic environment.
Diagnosis: Normal Melt vs. Actual Death
Normal changes in a plant’s growth can easily be interpreted as the plant dying. Instead of tossing the hairgrass, check the substrate level first.
Here is how to determine a healthy melt from a failing plant.
| Observation | Normal Melt | Actual Plant Death |
|---|---|---|
| Blade Color | Old blades turn pale yellow or brown, but tiny bright green needles appear at the base. | The entire plug turns gray or translucent brown with zero new green growth. |
| Root Condition | Roots remain white and firm. They may begin spreading horizontally under the soil. | Roots turn black, mushy, and smell like sulfur if you pull a plug up. |
| Plant Anchoring | The plug feels firmly rooted in the substrate if you gently tug it with tweezers. | The plug floats away on its own or dislodges with the slightest water movement. |
Your plant is perfectly fine and just needs time. To speed up that recovery, you must see 2 specific conditions. If you see white roots and tiny green needles pushing through the soil, then you are in good shape.
Condition One: Deep Root Nutrition
Dwarf hairgrass relies heavily on its roots for sustenance. While the melting phase is troubling for most plants, hairgrass can focus on its root system to survive this phase and even rejuvenate.
When hairgrass is planted in regular sand or inert gravel with no nutrient aids, hairgrass will have difficulty finding the energy to recover. Hairgrass will melt stall and ultimately starve.
You need a nutrient-rich substrate. A high-quality active aquasoil is the best option for carpeting plants because it is soft enough for delicate runners to penetrate and is packed with the nitrogen and trace elements the roots crave. If you are using an inert substrate like sand, you must push root tabs deep into the substrate directly beneath your hairgrass plugs. Space the tabs about three inches apart to ensure the spreading roots have a constant food source.
Condition Two: Unobstructed Light at the Substrate Level
The engine that drives plant recovery is light. The main problem with carpeting plants is their position. Being located at the bottom of the tank, dwarf hairgrass is the furthest plant from your light.
The greater the water depth, the greater the amount of light that is filtered out. The more floating plants, large hardscape pieces, or broad-leafed plant stems that cover your hairgrass, the more melt will become die off. The new submerged needles will require strong direct light to be able to photosynthesize and spread.
Next Steps for the Aquascaper
After checking that your roots are healthy and there are no obstructions to your lighting, there’s just one other practical task that remains.
Grab your curved aquascaping scissors and give the melting grass a haircut. Trim away as much of the dead, brown growth as you safely can without uprooting the plugs. Leaving rotting organic matter in your tank will only invite algae, which will quickly smother the tiny new green needles trying to emerge.
Clear away the trimmings with a small siphon. Check your water parameters. Keep your light cycle consistent.
Next all that is left to do is wait! If you look closely at the soil in the coming weeks, you will see a network of bright green runners spreading across the dark aquasoil. That is the end of the melt, and the start of your carpet.
