Aquarium plants melt when they drop their leaves in the weeks after planting. It looks like the plant is dying, and usually it isn’t. Most shop plants were grown out of water, and those leaves can’t survive submerged, so they die back while new underwater leaves replace them. Leave the roots in place and wait.
Why aquarium plants melt
Most plants come from the nursery in their emersed form, grown with their leaves in the air. Buce Plant explains why: grown that way, plants grow much faster, stay largely free of algae and survive shipping better. Aquasabi says they then have to adapt to life underwater, which takes quite a bit of time, and it isn’t unusual for a plant to lose all its old emersed leaves on the way.
That leaf loss is the melt. Buce Plant says the emersed leaves aren’t adapted to survive underwater, so they slowly decompose while new submerged leaves grow to replace them.
Tissue-culture plants
Plants sold in cups from in-vitro culture behave a little differently. Aquasabi says they are generally somewhat more sensitive than potted emersed plants, but usually need only a few days to get used to a tank. Expect slow or stalled growth and perhaps the loss of adult leaves, especially in Cryptocoryne and Bucephalandra. Brown leaves already in a Cryptocoryne cup are normal, Aquasabi adds.
Other things that cause melt
The move to water is the usual cause, but not the only one. These are the others the sources name:
- Rough handling. Buce Plant says damage in shipping, or fish chewing the leaves, can set it off.
- An uncycled tank. Buce Plant warns that nutrient-rich aquasoil can leach ammonia into a new tank, and recommends planting into a cycled one.
- Too little light or too few nutrients. Once a plant has made the switch, Buce Plant says melt can point to a nutrient shortage, and that too little light can cause it too.
- Sudden changes. Horizon Aquatics says crypts are sensitive to sudden changes in pH, temperature, hardness and light. Buce Plant adds that a big switch in water chemistry, or very hot or cold water in a large water change, can trigger mass melt in a carpet.
- Moving the plant. Buce Plant says a plant moved before it has rooted has to start again, and may melt while it does.
Which plants melt
| Plant | What the sources say |
|---|---|
| Cryptocoryne | Almost all species do it (Buce Plant), often within days of going into a new tank (Horizon). It is so common that it has its own name, crypt melt. Cryptocoryne parva is the exception: Buce Plant says it usually doesn’t melt like the others. |
| Bucephalandra | Tissue-culture plants may lose their adult leaves (Aquasabi). |
| Monte Carlo and other carpets | Some melt at first is normal, and new growth replaces it if conditions are right (Buce Plant). |
| Hornwort | Sheds its needles after sudden changes, temperature swings or a move (Buce Plant). It grows only underwater, so it has no emersed leaves to lose. |
| Anubias | Tropica says Anubias grow so slowly they barely notice being submerged. If one loses leaves, check the rhizome isn’t buried: Tropica says that makes the whole plant rot and die. |
The one mistake that kills the plant
Digging it up.
A melting plant usually is not dying, so there is nothing to rescue. Horizon Aquatics says the roots often survive crypt melt and new leaves will sprout as long as they are healthy, and Buce Plant says a crypt with healthy roots that isn’t moved should show new growth within a few weeks. Pulling a melting Cryptocoryne wendtii out to inspect it, or moving it somewhere it might be happier, sets that back.
The same applies to rhizome plants. Aquasabi says even a bare rhizome, with no leaves or roots left, can grow back into a whole plant if it is intact. Keep it attached to its wood or rock and wait.
What to do while it melts
- Remove the dead leaves. Horizon Aquatics says decaying leaves can cause ammonia spikes, and Buce Plant says rotting leaves add nitrate that can lead to algae.
- Leave the roots and rhizome in place. This is the whole trick.
- Keep conditions stable. Horizon advises avoiding further changes for a few weeks.
- Wait. Aquasabi’s advice is not to give up on plants too early, because they usually bounce back.
How to reduce it next time
You can’t always stop melt, but Buce Plant gives several ways to cut it down:
- Plant into a cycled tank, so ammonia from fresh soil isn’t added to the stress.
- Trim off a few emersed leaves before planting, and remove the rest once plenty of submerged growth has appeared. With crypts, Buce Plant suggests cutting off all the emersed leaves, except on Cryptocoryne parva.
- Don’t move plants once they are in.
- Keep the routine steady: feeding, water changes and light hours.
- Add CO2 if you can. Buce Plant says it shortens the transition, and helps melting crypts bounce back faster.
Aquasabi adds two tips for a new tank: start with only a little fertiliser while the plants adapt, and plant at least one group of fast stem plants that are already in their submerged form, as an early warning of any deficiency.
How long it lasts
For potted plants, weeks. Aquasabi’s timeline for a new tank says plants should have taken on their submerged form, rooted and started growing visibly by week three. Buce Plant says crypts that keep healthy roots should show new growth within a few weeks. Tissue-culture plants are quicker, usually a few days according to Aquasabi.
When it is not melt
Melt happens shortly after planting and affects the existing leaves while new growth appears. If an established plant starts declining months in, that is a different problem and the place to look is light, nutrients or CO2 rather than transition. Our yellowing leaves page covers how to read the pattern.
Questions about melting plants
Why are my aquarium plants melting?
Usually because they were grown out of water. Buce Plant says emersed-grown leaves aren’t adapted to life underwater, so they decay while new submerged leaves grow. Sudden changes in water, light or temperature, and moving a plant, can also set it off.
How long does plant melt last?
A few weeks for most potted plants. Aquasabi expects plants in a new tank to be growing visibly by week three, and Buce Plant says crypts with healthy roots show new growth within a few weeks.
Will melted aquarium plants grow back?
Usually. Horizon Aquatics says the roots often survive crypt melt and new leaves sprout while they are healthy, and Aquasabi says even a bare rhizome can regrow if it is intact.
Should I remove a melting plant from the tank?
No. Take off the dead leaves and leave the roots where they are. Moving a plant before it has rooted makes it start again, Buce Plant says.
Can you prevent plant melt?
You can reduce it. Buce Plant’s advice is to plant into a cycled tank, trim emersed leaves before planting (except on Cryptocoryne parva), leave plants where you put them and keep conditions stable.
Sources: Aquasabi, Fertilization during the cycling phase; Aquasabi, Appearance of in-vitro plants; Aquasabi, How to trim and divide aquatic plants; Buce Plant, How to prevent aquarium plant melt; Buce Plant, How to prevent Cryptocoryne melt; Buce Plant, How to grow aquarium carpet plants; Buce Plant, Hornwort (shop listing); Horizon Aquatics, Cryptocoryne and crypt melt; Tropica, Anubias barteri ‘Coffeifolia’; Tropica, Anubias gracilis.