Cryptocoryne wendtii Photo: Tanja Pirenz
Cryptocorynes are usually shade plants, but not particularly sensitive to light. However, they are often sensitive to sudden, major changes. With changed light or water values, changes in the water change rhythm, sometimes even after larger water changes, the leaves seem to rot extremely quickly.
This behavior is called cryptocoryne rot. However, this is not a disease, the cryptocorynes simply change their leaves, similar to deciduous trees. The roots remain completely undamaged. As a rule, after a few weeks, the plants look the same as before.
Cryptocorynes are sensitive to any change in their environment and can react to this by changing leaves.
If the roots rot, it is not cryptocoryne rot. In such cases, as with other plant species, the substrate usually rots and must be replaced with a better substrate.
Cryptocorynes often take a long time to get used to. It can take 1 to 2 years before they form a stable population that does not collapse again and again. During this time, cryptocoryne rot occurs again and again, often for incomprehensible reasons.
Cryptocorynes reproduce by forming stolons.
Cryptocoryne parva
Cryptocoryne wendtii brown Photo: Tanja Pirenz
Like all cryptocorynes, Cryptocoryne parva reproduces by forming runners.
It is a matter of time, how fast and how many offshoots it forms.
Since Cryptocoryne parva grows very slowly, it sometimes takes a long time for stolons to form.
Otocinclus on brown Cryptocoryne wendtii:
cryptocoryne blight
Cryptocoryne becketti Photo: Stefanie Prinz
Cryptocorynes are able to return the nutrients contained in the leaves to the root nodules in no time at all. The leaves seem to be rotting. Within a few hours or days, all the leaves can dissolve.
This behavior also occurs in natural locations. In Southeast Asia, where they are native, the salinity of the water is significantly diluted at the beginning of the monsoon. A short time later the streams swell to rivers. The cryptocorynes protect themselves by reducing the surface area of water contact with their leaves, but then come back as soon as the salinity rises again.
Cryptocorynes also react to a change in salinity in the aquarium, not to the absolute height. Cryptocorynes, which have found a new home in an aquarium, can therefore be replanted within a biotope-stable tank without a leaf being dropped.
Cryptocoryne wendtii Photo: Norbert Heidbüchel
However, not only does a change in salinity lead to cryptocoryne rot in the aquarium, but basically any change can trigger the rot, changes in light colour, light intensity, water temperature, etc.
In the case of sensitive cryptocorynes, the water may also have to be changed in small quantities every day if they are not to react with rot.
Possibly adding iron can prevent, slow down, or end the rot. This is indicated by experience with Fetrilon and fertilizer tablets especially for cryptocorynes.
New leaves usually grow back quickly and the plants recover. You can often see the beginnings of new leaves while old leaves are still dissolving.
Conjectures about crytocoryne rot
Cryptocoryne wendtii Photo: Norbert Heidbüchel
Larger and older leaves are probably more sensitive and rot earlier than smaller and younger leaves. The opposite appears to be true for entire stocks. Apparently, older stocks are not as sensitive as younger stocks. Older stocks can cope with environmental changes that are already causing younger stocks to collapse. So when a stand suffers from cryptocoryne rot, the larger, older leaves are affected first.
As soon as translucent spots form when viewed from the underside of the leaves, it is not long before the plant begins to generate oxygen bubbles in these areas, which rise like a fine string of pearls. If you don’t quickly help with Fetrilon or fertilizer tablets for Cryptocoryne, at least this hand is lost.
Normally the leaves have a silky smooth surface when viewed in the directed light of an HQI lamp at an angle of about 45 degrees. When they are about to outgas, the surface of the leaves will become dull overnight. Then the plant has already started to “pump out” the contents of the leaves.
Cryptocoryne rot © Norber Hedibüchel
If oxygen bubbles rise up like strings of pearls on leaf edges that are obviously damaged from the outside, eg by fish nibbling, there is usually no danger. Normally, in such cases, even without additional fertilization, only the damaged leaf dies.
A crytocoryne rot can be produced within 24 hours with 3 mg formalin per liter of aquarium water. With a maximum conductance of 100 µS, the decay process can also be triggered by reducing the conductance by at least 20% within one hour.
An incipient outgassing of oxygen can be stopped in very soft water of a maximum of 100 µS with a quantity of 2 ml Fetrilon per 100 liters or a sachet of Fetrilon per 1 liter of aquarium water. With higher conductance values, the dose may have to be increased.
Within the next six hours, the vast majority of leaves will recover. However, it will not be possible to return the translucent light spots that have formed irregularly over the entire leaf surface to their original color. The bright spots are henceforth those most at risk of pitting and outgassing. Presumably these places are incurably destroyed.
Because iron-containing fertilizers work, it is natural to speculate on iron deficiency or nutrient deficiencies in general. Iron is required for photosynthesis and is used to build the leaf green. If there is a lack of iron, the leaves become lighter and the colors are no longer as rich and strong. That explains perhaps the observation with the leaves «shiny» and «dull». If there is a lack of iron, the veins of the leaves can also become lighter and protrude to the point of yellow leaves. In total iron chlorosis, leaf green no longer exists.
Hypothesis 1: When diluted in water, Fetrilon decomposes into Fe x 2 EDTA and Fe(OH)3. The latter is finely suspended like powder. This decomposition already begins in concentrated solution and leads to the well-known discoloration of the solution. This powder may react with the affected areas.
First, a bacterial cloudy water develops. Then the exoenzymes of the starving bacteria take hold. e.g. B. proteases attack the surface of cryptocoryne leaves.
Hypothesis 2: Cryptocorynes store iron in their leaves. However, the oxygen produced by the leaves should be bound by the iron to such an extent that no outgassing can occur in molecular form. If too little iron is bound in the leaves, oxygen can escape from the areas with the translucent bright spots and destroy the cell structure.
However, it is unclear whether increased iron intake, or some other mechanism associated with iron intake, mitigates crytocoryne rot.
Iron deficiency is often a multiple deficiency of several trace elements. The EDTA in the Fetrilon also recovers other lost plant nutrients and makes them available again for the plants in the short term. An increase in manganese can often be measured after Fetilon fertilization, although Fetrilon does not contain any manganese.
This even contradicts a common theory according to which iron fertilization unilaterally displaces manganese. This does not appear to be the case for Fetrilon
Apparently, the EDTA also mobilizes enough manganese back again, even if this should not be the case according to theory.
Unfortunately, crytocoryne rot cannot be prevented by constantly increasing the iron content in the water. You can only try to stop the onset of rot by adding more iron. If the iron content is already high, an additional iron intake does not seem to help. The rot does not seem to be a pure consequence of iron deficiency, because it also occurs in tanks in which there is actually enough iron. To complicate matters further, not every iron fertilizer seems to help. There is evidence that fertilizers with divalent iron do not help.
implement cryptocorynes
Red Fire dwarf shrimp in Cryptocoryne Photo: Norbert Heidbüchel
Transferring Cryptocoryne from one location in an aquarium to another location in the same aquarium with similar lighting conditions often works even if the roots are damaged.
If cryptocorynes are transferred to a completely different tank, there is a risk that all the leaves will be shed. However, this does not mean that the plants need to be cared for. Rather, this reaction is probably genetically predetermined by the seasonal conditions of the original countries of origin in order to protect themselves from torrential floods when the rainy season begins.
Between these two extremes, there are many intermediate stages. The more the old and new locations are similar, the greater the chances that moving will not cause any problems. The more clearly the old and new locations differ, the more likely cryptocoryne rot occurs.
For transplanting, the plants are undermined with the finger and slowly lifted out of the ground so that the rootstocks are damaged as little as possible. Then offshoots are carefully separated and, if necessary, the roots are shortened by up to 2/3. The plant is then used at the new location so that the roots are as completely as possible in the ground. With species that react sensitively to the shortening of the roots, you can carefully unroll the roots and replant them.
Cryptocorynae and Vallisneria
Cryptocoryne wendtii Photo: Norbert Heidbüchel
It is said again and again that Cryptocoryne and Vallisneria cannot be kept together in one aquarium. According to some information, Sagittarians cannot be kept together with Cryptocorynae either.
Reasons for this are not known. Studies have not been able to find any antibodies that one species releases against the other species.
However, there are also many reports that Cryptocoryne and Vallisneria, eg V. spiralis and C. wendtii, can be kept together in the same tank.
Cryptocoryne wendtii Photo: Norbert Heidbüchel
The plant species probably only have different requirements. Socialization can be successful if the conditions are midway between the optimal conditions of both plants, but still within the respective tolerance range. When conditions are skewed towards a plant, it becomes the winner…