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Issue: Jun 2017

Bottom of the Tank: Driftwood Catfish

Author: Joshua Wiegert

Driftwood catfish, also called wood cats, are a small group of fishes from the family Auchenipteridae found throughout the Amazon. Most of these are small species, making them excellent for aquariums. The family, which also contains a handful of larger fishes, has been divided into two subfamilies, Auchenipterinae and Centromochlinae; the former has been traditionally of much less interest to aquarists than the latter, though this is gradually changing.

Livebearing Catfish

Within Auchenipteridae there are about 125 fish spread across nearly two dozen genera. This is a truly diverse family, with incredible variability in appearance among its members. While not technically livebearers, wood cats are unique among catfishes in that they practice internal fertilization. The male’s anal fin sports a modification that serves a similar role as the gonopodium in livebearers. Males will fertilize the female, who will lay eggs several days later. It is not uncommon for mature females to lay fertile eggs without a male present, even among species that have not been bred in the aquarium. These females are simply laying eggs that were fertilized previously, much like a single female guppy dropping fry a week after purchase.

Honeycomb Catfish (Centromochlus perugiae)

Perhaps the best known of the wood cats is the honeycomb catfish (Centromochlus perugiae). Until 1998, this fish was placed in the genus Tatia, and many resources still list it incorrectly as Tatia perugiae. A small fish, the honeycomb cat reaches a maximum size of only about 2 inches (5 cm). C. perugiae is covered in a pattern of large black spots separated by a white network, hence the name “honeycomb.” They’re a truly pretty fish, with a delicate pattern. Their native range runs throughout Peru, Ecuador, and Colombia. While the species name suggests that they were named for Peru, where they do occur, they were actually named for ichthyologist Albert Perugia.

These are really great little fish that are unfortunately not seen in the hobby very often, and they have a rather unfortunate reputation for being both expensive and delicate. In my experience, these fish do much better in a small group. They truly need to be kept in tanks with a lot of hiding spots, such as driftwood and rockwork with many crevices. They’re often kept in heavily planted tanks, which is fine, but the setup also needs to include some “hardscape” hiding spots. Honeycomb cats are generally adaptable to different water parameters, but they do much better at a slightly acidic pH and lower hardness. They do prefer a higher temperature, as they are susceptible to ich and other infections at lower temperatures; I usually keep these fish at about 78° to 80°F (25° to 27°C). C. perugiae is very sensitive to poor water conditions. Nitrate levels must be kept low, and they require higher than average oxygen levels, which can be aided by the addition of a powerhead or other device. They’re more likely to thrive with some current in their tank.

These little catfishes are peaceful and shy, generally only coming out when the tank lights are off. Because of this, many aquarists fail to understand how they feed. In the wild, they skim small insects from stream surfaces at night. They do not hunt along the bottom, and they do not eat well during the day. A high-quality floating food is a must, and it should be given to them when the lights are out or at least dimmed. While they’ll often eat flakes, floating insect-based foods are great, frozen or not. They’ll make short work of populations of mosquito larvae. Feeding them as you would a Corydoras, with a sinking pellet, will likely result in some very hungry cats, and eventually worse.

The honeycomb catfish has been successfully bred in home aquaria, and its breeding method is somewhat unique. Among the driftwood cats we’ll discuss, this is undoubtedly the easiest species to breed in the home aquarium. Several days after being fertilized, the females will enter a small cave or other crevice to deposit about a hundred eggs. These eggs are guarded by the female until they hatch, about four or five days later. The eggs may be preyed upon by other fish in the tank.

When I’ve bred this fish, I’ve used small pieces of PVC pipe as caves. I put a finger over each end of the water-filled cave, lift it out with the female, and relocate it to a new tank; I don’t think the female even notices sometimes. Once the eggs hatch, the female should be returned to the main aquarium or she may eat the fry.

The fry develop quickly and are tiny eating machines. Surface foods, including powdered fry formula, brine shrimp nauplii, and ground flakes are all eaten with gusto—but again, only at night. Heavy feedings may lead to deteriorating water conditions, so large, frequent water changes are a must.

Galaxy Wood Cat (Tatia galaxias)

The genus Tatia, also in the subfamily Centromochlinae, contains a number of fishes that are of interest to aquarists. The most commonly encountered of these is supposedly T. galaxias, however, many of the T. galaxias imported are actually T. intermedia. Both species are superficially quite similar, especially when younger; however, T. intermedia will lose its spots as it ages, and it reaches a size of nearly twice that of T. galaxias.

The true galaxy wood cat, T. galaxias, is a striking black fish covered with small white dots. It will reach a maximum size of just about 3 inches (7.5 cm). T. intermedia, however, will reach about 5 inches (12.5 cm). These fish usually have many more spots than T. galaxias, and the spots tend to be more gray than white in color. Regardless of species, their care is quite similar. Like the honeycomb catfish, they require clean, well-oxygenated water, with plenty of hiding places. Feeding should be done only at night, though both of these fish seem to be a little more forgiving about daylight than the honeycomb.

Both T. galaxias and T. intermedia have been bred in captivity, and they are easily sexed, as with Centromochlus. However, unlike Centromochlus, eggs are typically laid in a mass in the water column and sink to the bottom. Females may guard the eggs for a brief period.

Ninja Wood Cat (Tatia musaica)

A true beauty of the genus, the ninja wood cat (Tatia musaica) is only rarely seen, and often at a very high price. I don’t know where the common name comes from, but I assume some marketing-minded importer just really liked the word “ninja.” The pattern of these fish reminds me of an orca—dark black on top, with a white underbelly, and patches of the two mixed in between. A very small fish, it won’t reach more than about 2 inches (5 cm).

A bit more delicate than the other Tatia species above, T. musaica is completely intolerant of poor water conditions. I can find no reliable sources indicating that this species has been spawned in the aquarium, though reproduction is presumably similar to other members of the genus.

Happy Driftwood Catfish (Trachelyichthys exilis)

The subfamily Auchenipterinae contains the bulk of the driftwood catfishes, although these fish are seldom seen in the hobby. Slowly, this is beginning to change, with many new imports from this group appearing. The best known of these is Trachelyichthys exilis, the happy driftwood catfish. T. exilis reaches a size of about 3 to 4 inches (7.5 to 10 cm). Its body form is pretty typical of the Auchenipterinae: a streamlined, midwater catfish shape with an elongated anal fin. Similar to the other driftwood cats, the first rays of this fin are modified in males. These fish are generally a gold color, with dark spots covering the body.

Happy driftwood cats are schooling fish, with small groups taking shelter in caves or other structures during the day. They’re far less shy than other driftwood catfishes, with food quickly luring them out of hiding. It’s really fun to drop food into a seemingly empty tank and watch an explosion of these catfish emerge from every hiding spot imaginable (and sometimes even some spots that aren’t).

Breeding T. exilis isn’t particularly troublesome and is quite similar to the previously mentioned species. However, the females will drop a handful of eggs at a time, usually scattering them throughout the tank. Fisher’s Wood Cat (Trachelyopterus fisheri) One of the more interesting catfish I recently worked with was

Fisher’s Wood Cat (Trachelyopterus fisheri)

This is one of the larger wood cats, reaching a maximum size of nearly a foot (30 cm). Despite their relatively large size, they are quite shy, but I found they could be coaxed out by keeping them in larger numbers. Two or three simply vanished into the tank, but a dozen were quite active and schooled constantly, regardless of the time of day.

They’re a dark, golden brown, with a maze of black lines across the body. Their body shape is very stereotypically catfish, but unlike most cats, they’re constantly on the move in the midwater. Like the other driftwood cats, expect them to ignore food on the bottom and instead opt for surface foods (and woe to any insect on the surface with a dozen of these below).

Care should be taken with the maximum size of this fish. While they were quite peaceful for me, I sold them all before they reached more than about 4 to 5 inches (10 to 12.5 cm), and I imagine that a fully grown specimen would not turn down the chance to make a convenient meal out of a small tankmate.

Wallace’s Shoehorn Catfish (Tetranematichthys wallacei)

Wallace’s shoehorn cat (Tetranematichthys wallacei) is an interesting member of the group. These fish rely strongly on camouflage, and they look quite a bit like large, dead leaves. This fish is sometimes imported under the name T. quadrifilis, but almost all of the shoehorns exported are likely T. wallacei. These fish reach a maximum size of about 7 to 8 inches (18 to 20.5 cm).

Aquariums for shoehorns should have a softer substrate rather than gravel, as they spend a lot of their time lying on it, mimicking a dead leaf. Driftwood and other hiding places are a must, and oak, beech, or other hardwood tree leaves are a good choice for providing shelter at the bottom. These leaves will also release tannins, which will lower the pH and stain the water brown, something shoehorns love. These fish differ from other members of the group in that small fishes make up most of their natural diet. They’ll quickly adapt to any good pellet food, but they should absolutely not be kept with anything mouth-sized. Though peaceful, they should not be housed with smaller fish at all. Males can be sexed by an extended dorsal fin. There are no confirmed reports of successful breeding of this fish in the aquarium.

Ogre Driftwood Catfish (Trachycorystes trachycorystes)

Rounding out this look at the driftwood catfishes is Trachycorystes trachycorystes, the ogre driftwood catfish (not to be confused with the ogre catfish, Asterophysus batrachus). These are unique wood cats, with bodies reminiscent of Raphael catfish. However, they’re jet black. The mouth is front-facing, and big. This fish reaches a maximum size of about 14 inches (36 cm), and it is apparently a food fish in Brazil and Venezuela.

While they can be quite shy in the aquarium, they are definitely predators and not to be trusted with anything smaller than they are. About a year ago, I received a half-dozen of these fish. They were definitely ugly, but I was soon to see where they really got the name “ogres.” They wedged themselves into any cave available in the tank and were seldom seen thereafter. So I forgot they were in there and put a batch of about a hundred 3- to 4-inch (7.5- to 10-cm) pearl gouramis into the tank (when you’re unpacking dozens of boxes of fish, these things sometimes happen). The next morning I could see every single one of the ogres, as they were now too fat to fit into any of the caves. Of the pearl gouramis, however, there were only two or three left.

A Diverse Family

The driftwood catfishes represent a huge spectrum of body types and behaviors, from tiny, peaceful fishes like the honeycomb driftwood catfish to monstrous eating machines like the ogre driftwood cat. While their shy natures can make them less appealing to casual aquarists, most species quickly adapt to aquaria, as well as to their keepers’ feeding schedules. With a little work, keeping these catfish can be a truly rewarding experience.

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