Why is My Cryptocoryne Pot 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 is a common phenomenon with cryptocorynes, and it is often called “crypt melting.”

Crypts and many other aquatic plants are extremely sensitive to changes in water quality. As such, they absorb the existing leaves to adjust to changing conditions. They “eat” the old leaves, which gives them energy to make new roots and create new leaves that can absorb nutrients and light.

Why is my new Crypt plant dying?

Most often, crypt melt occurs in plants that have just been purchased. Emersed-grown aquariums are commonly grown on commercial farms. This means that the leaves and roots are left in open air, while only the roots are watered. Because leaves can access light and carbon dioxide (CO2) easier from air than water, this allows them to grow faster. Growing the plants out of water also protects the leaves from algae growth, pest snails, and fish diseases.

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. The emersed leaves are usually large and broad. Submerged leaves are smaller and more delicate. 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. You should not discard your cryptocoryne if it starts melting after you have planted it at home. You should start to see tiny shoots within weeks, as long as the roots are healthy and it isn’t moved after being planted. 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 lead to nitrogen spikes and algae growth. It’s best not to remove them until your cleanup crew eats the leaf.

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

You have two options to survive the transition period: you can either trim the leaves individually as they melt or you can trim them all back to the substrate. This allows the crypt to concentrate on creating new leaves and not trying to save old ones. The aquarium environment should be kept as stable as possible. Wait several weeks for the cryptocoryne plant to return. 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. You can add floating and fast-growing plants as well as stem plants to reduce algae growth.

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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