Aquarium Cryptocoryne Plants

Although the proper scientific name of this aquarium plant genus is Cryptocoryne, they are commonly referred to as “crypts.”

Cryptocoryne undulate: This species occurs in central Sri Lanka. It is second only to C. wendtii in being the easiest crypt to grow in aquaria. Photo by Robert Paul Hudson
Cryptocoryne undulate: This species occurs in central Sri Lanka. It is second only to C. wendtii in being the easiest crypt to grow in aquaria. Photo by Robert Paul Hudson

The name Cryptocoryne is a funny-sounding name for a group of plants that have been popular in the aquarium hobby for decades. The word comes from the Greek word krypto, meaning hidden, and koryne, meaning stick, referring to the hidden (by the basal wall) spadix (an inflorescence, or a cluster of flowers on a stem, where the small flowers are crowded on a thickened, fleshy axis) in the flower structure. There are 58 recognized species and of these less than a dozen are suitable for the aquarium. Of those suitable species, there are several cultivated variations (known as cultivars) that produce different leaf colors and shapes, and there are regional habitat variations of species as well.

Cryptocoryne Anatomy

The spadix, a flowery structure typical of the family, is the “stick” that contains the male and female reproductive organs. The stamens (a pollen-bearing organ in a flower) are located in the top of the spadix, while the stigmas (the free upper part of the style — the slender part between the stigma and the ovary — of a flower where pollen falls and develops) are at the bottom close to the chamber cavity called the kettle. Pollen and eggs also reside in the kettle, which has bright colors that attract insects for pollination. Many of the Cryptocoryne species would be impossible to distinguish if not for the flower structure, which does not bloom underwater.

These leaf shapes range from long and straplike to ovate (round or oval), and even grasslike, to very small and spoon shaped. Typically, the colors are dark earthy tones of green, red and bronze and are prized in the aquarium for distinctive groupings or rows.

Typical habitats of Cryptocoryne are meandering rivers in lowland forests. They also live in seasonal flood pools or flooded river banks. Although the proper scientific name of the genus is Cryptocoryne, they are commonly referred to as “crypts.”

Most of the more common aquarium species come from Sri Lanka, including Cryptocoryne wendtii (including several varieties and hybrids), C. walkerii (otherwise known as C. lutea), C. undulate and C. becketii (including the variety known as “petchii”). These grow in small streams in soils of various types (sandy loam, clay, leaf litter) and mostly in soft acidic waters.

These species adapt readily to the aquarium and tolerate a wider variety of water conditions than other Cryptocoryne species and have been mass-produced in plant farms worldwide. In recent years, additional species found in Malaysia, Indonesia, Sumatra and Borneo have been introduced to the hobby and while some are more challenging than others, all have proven to be suited to aquaria.

Cryptocoryne Care

Specific care requirements vary from one species to another. In general, most aquarium crypts are adaptable to moderately acidic to moderately hard water with three basic requirements: fertile substrate, system stability and clean water. These three requirements must be met in order to avoid “crypt-melt” syndrome. While these plants are often thought of as low-light plants, only a few species tolerate low-light levels. All crypts will flourish under more intense light.

Like other plants, crypts need light and nutrients in order to grow and develop to their full potential. Two or three watts of fluorescent light per gallon of water should be enough light for most species. The color of the light is determined by the Kelvin rating and is more for aesthetic benefit than plant growth. A good daylight bulb around 6500 K is my preference.

Another factor to be considered is the substrate. Like most rosette plants, crypts grow more vigorously in nutrient-rich soils. Typical neutral sandy soils or gravel will prove to be of no nutritional value for these plants. While most commercial aquarium substrates are clay gravel, which provides iron and other minerals but are free of organic material that will break down. Although these substrates provide no nitrogen or other macronutrients, they are considered safe because they are inert. Over time as an aquarium matures, organic material settles to the bottom of the substrate and provides a good source of nitrogen and some other macronutrients for the plants. This is the reason you often see Cryptocoryne species thriving in old aquariums that have subdued light and receive no supplemental fertilization.

Crypt Melt

Cryptocoryne species may suddenly have a complete meltdown, where all or most of their leaves simply disintegrate. The exact causes and circumstances of this has never been fully established. It has even been referred to as a disease.

It is known that various environmental conditions can trigger it. Sudden changes in temperature, water quality, nitrate or ammonia levels and transplant shock all may set off this condition. It has been observed happening in natural habitats during seasonal changes and periods of reduced rainfall. It could very well be a defense mechanism. If left undisturbed in stable conditions, the rootstock, or rhizome, will usually totally regrow new leaves within a few weeks to a few months.

The biggest mistake hobbyists make when this malaise strikes is thinking their crypts are dead and then preceding to throw out what’s left of the plants.

Foreground to Middle Ground Crypts

The following six crypts work best if placed in the front or middle portions of your aquascape.

Cryptocoryne albida

This species is native to Myanmar and southern Thailand. This short plant has narrow lanceolate (tapering to a point; similar to a lance) leaves that range from light green to reddish-brown. It tends to respond more favorably to soft water, and a nutrient-rich, slightly acidic substrate accelerates its growth from a snail’s pace to noticeable. It is best planted in the tank foreground not too close to other plants. This plant is not often available commercially in the United States, but it is occasionally imported.

Cryptocoryne affinis

Occurring in the Malay Peninsula, this plant has been used in aquaria for more than 50 years. It is quite easy to grow, but the availability of it comes and goes. The reason for this is that C. affinis is not an easy plant to propagate and mass produce; therefore, nurseries often opt not to grow the plant.

This attractive species varies in height from 4 to 12 inches, depending on conditions in the tank. The top side of the lanceolate leaves is a bright green with lighter vein patterns and often bullate (puckered; inflated like a blister), while the underside is bluish-red. Cryptocoryne affinis is a fast grower, as far as crypts go, under conditions to its liking. But it is prone to melting if the aquarium is not kept stable.

Cryptocoryne walkerii

(formerly C. lutea): Like C. wendtii and other Sri Lankan crypts, C. walkerii ranks as one of the crypts that should be in every planted aquarium. It is easy to grow, versatile and very attractive in groups. It readily propagates from runners and grows at a moderate pace under medium to intense light.

Cryptocoryne parva

From Sri Lanka, this is the smallest Cryptocoryne sp. and reaches only 2 or 3 inches tall. It has little spoon-shaped leaves. It can adapt to hard or soft water and needs only moderate light. It is a wonderful foreground plant with one drawback: it grows very slowly. More intense light produces more horizontal growth, while lower-light levels induce the plant to grow taller.

Cryptocoryne wendtii

This is probably the most widely known and used Cryptocoryne species. Cryptocoryne wendtii comes in a wide range of colors and sizes. Red, green, bronze and brown are standard colors for this Sri Lankan native. Genetically mutated strains with variegated colors have been produced, with the latest one being the ‘Florida Sunset,’ which has leaves of multiple shades of red, yellow, orange and white.

Leaf shape and size variations of C. wendtii include narrow, broad, tall and short variants. It is unquestionably the easiest Cryptocoryne species to grow in aquaria. This species is suitable for the middle and background areas of the planted aquarium.

Cryptocoryne undulate

This species occurs in central Sri Lanka. It is second only to C. wendtii in being the easiest crypt to grow in aquaria; it is highly adaptable. Color with this species ranges from a medium green to a dark brown or red. Plant this species in groups and in the middle ground of the aquascape.
Middle and Background Crypts
This crypt group is at its aesthetically most pleasing when thoughtfully planted in the middle and background areas of the aquarium.

Cryptocoryne cordata var. blassii

There are several varieties of C. cordata, but C. cordata var. blassii (of the Malay Peninsula) is the variety most commonly seen in aquaria. Its large round leaves, olive green topside and beet red underside make it an attractive plant for the mid to rear of the aquarium. It can take several weeks or even months for the plant to become established after planting. Once it becomes established, growth tends to be more vigorous. It seems adaptable to hard water but may do better in soft, slightly acidic conditions.

Cryptocoryne crispatula var. balansae

From India and Thailand, this plant is usually sold by the name “balansae,” but it is considered to be a variant of C. crispatula. Balansae can definitely take its time when it comes to getting established, but it is worth the wait. Its long, straplike, deep green leaves grow up to 16 inches and often have a wonderful dimpled surface. It does best with moderately hard water and bright light. The leaves grow straight up and arch at the water surface. Arranged in thick stands, it creates an impressive visual statement.

There are three crypts in this group that look alike: C. ciliate, C. pontederifolia and C. moehlmannii. The latter two even grow side by side in the same region but each are a distinct species.

Cryptocoryne pontederifolia

Cryptocoryne pontederifolia is a striking light green plant with good-size ovate leaves that are broader at the base and come to sharp, elongated points. The species originates from Sumatra. Moderate to bright light is all it really needs. It is not a plant that does well if frequently uprooted and replanted. Pick a spot and leave it there, and it will grow in nicely.

Cryptocoryne moehlmannii

Almost identical to C. pontederifolia and from the same locality, this plant typically has less elongated leaves that may either be bullate or have a smooth shiny surface. Its growing requirements are the same as other crypts in this group.

Cryptocoryne ciliate

From India and New Guinea, this is a durable, highly adaptable plant. It grows in a variety of water conditions, including brackish. Strong light allows the plant to grow at a reasonable rate. It adapts well to growing above water in paludariums.

Cryptocoryne usteriana

This plant, from the Philippines, is attractive because it grows well in hard water with little effort or special care. It can grow fairly large with straplike leaves draping across the water surface. Typically, the leaves are dark green and puckered on the top side with a dark red underside that stands out. A hybrid recently developed in Germany has red on both sides of its leaves. Cryptocoryne usteriana occasionally flowers underwater (it is the only crypt I’m aware of that does this). The plant grows quickly and readily reproduces by runners. One healthy plant could produce several new plants within a year. The plant is becoming more widely available.

Collecting Crypts

Crypts appeal to collectors and reach a whole new realm of admiration outside the aquarium. Collectors grow each individual plant in its own pot, with a special soil mixture and in only a few inches of water. They are grown in sealed containers to provide high humidity and better control of air temperatures. There are many species grown this way that will not grow in aquaria, and these species are very hard to come by. They are often traded between collectors and sometimes sold to a select group of people for hundreds of dollars. The goal is to bring each plant to bloom. To outsiders, the flowers are nothing spectacular. Interest in crypts is not shared by the average aquarium hobbyist either, but in the eyes of avid crypt fans, there is nothing more rewarding.

Something New

Irrespective of whether your looking for something simple or challenging — the Cryptocoryne genus has a plant for every aquatic plant enthusiast. As long as you are patient with these plants and are willing to allow them time to settle in and mature within your setup, you won’t be disappointed.

For the modern aquascaper who is constantly uprooting and rearranging plants, crypts are probably not the best choice. But for the hobbyist who is planning a garden for the long term — over a period of months or years — crypts are a good choice for their aquarium.

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