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Why is My Cryptocoryne Plant Melting?

You just planted your new cryptocoryne (or crypt) plant in the aquarium, and it looks perfect for the first few days. Then you notice that one or two leaves aren’t doing so well. Maybe they are turning yellow-brown, have large gaping holes, or are simply withering away. Soon the whole plant looks as bare as a maple tree in winter. This phenomenon is very common with cryptocorynes and is often called “crypt melt.” 

Crypts (and many other live aquatic plants) are very sensitive to major changes in their water, so they respond by absorbing their existing leaves as they adjust to the different conditions. The energy they gain from “consuming” the old leaves allows the crypts to create new roots and leaves that can once again gather nutrients and light in their new environment.

Why Is My New Crypt Plant Dying?

Crypt melt most frequently occurs in newly purchased plants. Commercial farms often produce emersed-grown aquarium plants, where the leaves are in open air and only the roots are covered in water. Leaves are able to access light and carbon dioxide (CO2) more easily from air versus from water, so this method allows plants to grow faster and larger. Growing the plants out of water also protects the leaves from algae growth, pest snails, and fish diseases.

aquarium plant farm

Plant farms grow their aquatic plants with the leaves out of water to encourage faster growth and minimize algae.

When you buy an emersed-grown cryptocoryne and put it fully underwater, the crypt must transition into a submersed-grown plant that is accustomed to absorbing light and CO2 from the water. All the thick, broad, emersed leaves usually melt away, and smaller, thinner, submersed leaves appear in their stead. At Aquarium Co-Op, we try to jumpstart this conversion process for you by giving our crypts plenty of light and CO2 injection before they are sold. However, if you see your cryptocoryne melting after you plant it at home, do not throw it away in the trash. As long as it has healthy roots and is not moved once planted, you should see little shoots popping up within a few weeks. Once you see new growth, make sure the crypt has enough lighting and root tab fertilizer to continue building submersed-grown leaves.

What should I do about the melted leaves? If you see a leaf is clearly melting, cut it off at the base of the stem near the substrate. Rotting leaves can sometimes cause nitrogen spikes or algae growth, so it’s best to remove them unless your clean-up crew members consume the dead leaf first.

Melting crypt

The larger, emersed-grown leaves usually melt first, and then smaller, submersed-grown leaves begin sprouting from the substrate.

Why Are My Established Crypts Melting?

Sometimes cryptocoryne plants may experience melting seemingly randomly, despite growing well in your fish tank for many months. As mentioned previously, crypts are very susceptible to environmental changes, such as shifts in:

  • Water quality
  • Water change frequency
  • Location (e.g., moving the crypt)
  • Lighting
  • Fertilizer dosing
  • Temperature during hot summers
  • CO2 injection
  • Fish food
  • Pollutants in the air

To survive the transition period, you can either prune the leaves one by one as they melt, or you can trim all the leaves back to the substrate. In theory, this latter method makes the crypt focus on making new leaves instead of trying to save the old ones. Keep the aquarium environment as stable as possible, and wait for several weeks to see if the cryptocoryne plants come back. Also, remember that while the crypts are melting or pruned back, your fish tank is more prone to an algae bloom because the crypts are no longer consuming as many nutrients in the water. Consider adding some fast-growing stem plants and floating plants to help minimize algae growth and keep the tank balanced in the interim.

crypt plant and barb fish

Do not immediately throw away a melted crypt, but rather wait at least three to four weeks to see if the plant will recover and send out new shoots.

To learn how to properly plant your cryptocoryne, read our article on the different techniques here:

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