Cryptocoryne: A how to Guide
Crypts (Cryptocorynes) have been a staple in planted aquariums since they were first imported in the 1930's. There are around 60 species known to science, and about 15 or so are available in the hobby. To this day many, many people have difficulty even keeping them alive. In this post, I'll show you how.
First, and by far the foremost, Crypts do not like to be moved. They'll respond with the famous 'Crypt Melt' where the leaves get holes in them and the plant collapses when moved from tank to tank. In a mature aquarium, they usually come back. In one that is new or in flux, they probably won't. But, once established, they are very hardy, long-lived plants. If you are one that continually rearranges your tank, Crypts probably aren't for you. Crypts aren't the first plants in your new aquarium; they're the ones you plant four or six months later. Crypts have to have stability.
The blanket needs of most Crypts are similar to that of my previous Sword Plant Primer, though most Crypts like it warmer. They need an enriched substrate and bright but diffused light, 77-82 degrees, pH neutral or slightly acid, moderately soft to moderately hard. To my experience, they grow better in soft, sightly acid water, though they are adaptable as long as extremes are avoided. One of the special substrates for planted tanks and/or gravel over a laterite layer is perfect for them. They have needs for iron and potassium, which those substrates provide. Liquid fertilization seems unneeded by them.
Crypts do better when they have warm feet. Low-wattage (25 or 50 watts) heating cables under the gravel improves their growth markedly. Evidence indicates that most aquarium plants benefit with one. A heating cable isn't essential to keeping Crypts, but it is always desirable, and your plants will thank you for it. You may see your Crypts put out a rare bloom or two in those circumstances.
Keep in mind that most Crypts available in the hobby don't like direct light. It should be diffused, perhaps going through a fine-leaved plant. Most of them won't die under bright light, but they won't grow, either, and leaf sizes could suffer.
Commonly, people put them at the base of stem (like Cabomba) and rosette (like sword) plants. Hailing from well-shaded jungle streams of SE Asia, Crypts thrive in dappled shade. Their colors counterpoint the bright greens with olive, reds, and darker greens. Primarily they reproduce via runners, with daughter plants on the nodes, but they have to be very happy, in a well maintained, well established, tank, to do so. Otherwise, their growth can be maddeningly slow.
Now some species
From Malaysia comes one of the first, and perhaps one of the easiest to keep, Crypts; C. affinis. Undemanding and commonly available, affinis reaches 10 inches. Its crinkled leaves vary in shade and color; usually they are a glossy light green, sometimes with a russet underside. It also has a wider temperature range than many Crypts - 72-82 degrees (22-28 C), and is one of the few that can be considered a fast grower, but will slow down as the plant ages. Affinis spreads via runners, but if the flower spike breaks the water and male and female plants are in the tank, it's possible to gather viable seeds. You'd have to pollinate the blooms yourself, with a soft brush, and be careful gathering the seeds, as fish find them tasty.
Another early aquarium species, in 1933 if memory serves, is the Thai native C. albida, which is also called C. costata. The Genus is currently under revision, so as of this writing either specie name is valid. A slow grower, C. albida doesn't move well at all, but with suitable lighting and a good substrate, it should grow well. Reaching from 10 inches to a foot, albida should be planted in groups, as solo plants look rather weak. The leaf color can be light green to red brown and are spear shaped. There are a few leaf cultivars (varieties), so if you want this plant, ask for it by name. Very bright light can cause it to shorten it's leaves. The Red Rasbora (Trigonostigma heteromorpha) likes to spawn on the underside of this plant, as they do in nature.
Resembling an elongated affinis, C. balansae is one of the most popular and decorative of the Crypts. Hailing from Thailand, balansae has long, light green, and highly-indented leaves. They look like green hammered metal. The leaves can reach 16 inches tall if the plant is very happy, but 12 to 14 is more usual. Balansae needs temperatures in the 77-82 (25-28 C) range. It reproduces by runners. I've never known it to bloom in aquariums. It's undemanding as to light, but grows and lives better in bright light. One of my favorite plants.
Beckett's Cryptocoryne, C. becketti, is one of the most commonly available species. A Sri Lankan, becketti reaches six inches. With a heated, nutrient-rich substrate, it grows very well. It spreads by adventitious plantlets (small shoots from its stem), creating an attractive bush of a plant. The dark green leaves are oblong and on long stems. C. becketti is a sturdy plant, and many bottom-dwelling fish will use it for cover. Temps are 77-82 (25-28 C).
One of the easiest to grow and thus quite popular, becketii's countryman C. walkeri is nearly always available. Single plants reproduce from shoots from it's base, creating a dense forest where little fish can hide. To my experience, it reaches 4.5 inches. There are several leaf varieties of it, some having brown veins and a reddish underside. In light, undemanding, in temps, 77-86 (22-30 C).
Called the Giant Crypt and rightly so, C. cordata from Thailand slowly grows to 16 inches or more and has large, ruffled, spear-like leaves. They are a sort of reddish olive green, with a deeper red underneath. The leaves are quite tough. Due to it's size and mass, it can be a centerpiece in mid-sized tanks. It reproduces both by plantlets from it's base and runners. Not terribly easy to keep (but well worth the effort), cordata needs a heated, nutrient-rich substrate to do well. It's also one that doesn't move well at all, so buy a few and hope one or two makes it. Established, though, in the right setting (moderate light) it should grow quite well. Temps are 72-82 (22-28 C).
On the other end of the spectrum, the Tiny Crypt C. parva reaches just two inches tall. It needs quite bright light to do well, and when well established, will carpet your tank, giving a lawn effect. The plant is easy to care for if given a good substrate and very bright light. Co2 is also quite helpful. Otherwise, it has a dismal survival record.Parva's dark green leaves are narrow swords on long stems. It prefers temperatures of 77-82 (25-28 C). Parva, from Sri Lanka, can also be used as a bog or marsh plant.
Available in a dazzling number of leaf varieties, C. wendtii from Sri Lanka is one of the standards of Crypt keeping. Leaves are normally dark to olive green, depending on the light it gets. Underside is usually sort of an orangish brown. It's also about the only Crypt that can be described as fast growing. Reaching 14 inches, it should be planted with four or five inches between plants. This allows it to grow into a pretty bush. It spreads by shoots and runners. Light can be moderate to very bright, but with all Crypts, it has to be one level all the time, as changes in light intensity brings on the dreaded Crypt Melt.
For those with hard water, C. undulata from India could be for you. The scientific name, undulata, describes the leaves perfectly, and are dark green with red stems. As it matures it can grow highly ruffled leaves more than 14 inches long, making it a dominant plant in most tanks. It needs bright, full-spectrum light, and a good, heated substrate. Temps are 72-82 (22-28 C).
Other Crypts include the large-leaved C. pontederiifolia, which can get very large, the foot tall, olive-leaved C. cilata, and the easily kept C. moehlmannii, which reaches up to eight inches tall.
I hope this post encourages you to give Crypts a try.
References: Ecology of the Planted Aquarium: A Practical Manual and Scientific Treatise For the Home Aquarist, Second Edition, 2003 (Echinodorus Publishing) by Diana L. Walstad.
Exotic Aquarium Fishes, 15th Edition, 1953 (Innes & Sons) by William T. Innes.
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