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Issue: November 2011

The Six-Barred Distichodus (Full Article)

Author: Kevin Thurston

THURS T 1111
The tiger-striped Distichodus sexfasciatus is an extremely large, active species that is a great acquisition for dedicated hobbyists.

When I was a young aquarist back in the 1960s, the pet stores carried little paperback booklets that sold for less than a dollar. This was when cory cats sold for 49 cents—more than the cost of a gallon of gasoline! When a neighbor was quitting the hobby, she gave me a stack of aquarium-related booklets that I was pleased to add to my collection. One was just a picture book of various aquarium fish that contained a nice photograph (taken by Gene Wolfsheimer) of a fish identified as Distichodus sexfasciatus—the six-barred distichodus. I was very impressed with that photo and was determined to own the fish someday, but it wasn’t until 1982 that I actually saw one firsthand.

Background

D. sexfasciatus is a characin that comes from the Congo River drainage, Angola, and the swampy drainage area of Lake Tanganyika. The fossil record suggests that the genus Distichodus was more widely distributed through Africa in the late Miocene to Pleistocene period (Stewart, 2001). According to Jacques Géry (and fishbase.org), they belong to the family Citharinidae, subfamily Distichodontinae, while others consider the subfamily to be a full family.

From the hobbyist perspective it is probably well thought of as one of those big tetra-type fish, like pacus. It is a beautiful fish with a color pattern suggestive of clown loaches and tiger barbs. There are six black bars on a red-orange body. Larger specimens have a faded red color on the body with bars that have a slightly greenish tinge and a red tail. When fully grown, the fish becomes totally gray.

There is a very similarly colored Distichodus sp., D. lusosso, which can be readily distinguished by its concave head shape. Outside of that, I’ve read that D. lussoso tends to have slightly higher counts for fin rays, scales, and bars.

I find the body shape of D. sexfasciatus to be more aesthetically pleasing than that of D. lusosso, so I’ve never kept D. lusosso,but the literature suggests that what applies to D. sexfasciatus also applies to D. lusosso, with the exception that D. lusosso does not get as big.

When viewed from the side, D. sexfasciatus appears to be a particularly robust fish, but when viewed from the front they seem fairly delicate due to being laterally compressed, nearly as thin proportionally as a discus or freshwater angelfish. The contrast can be surprising when seen for the first time.

Obtaining Distichodus sexfasciatus

D. sexfasciatus can occasionally be found in stores these days, usually at a size of about 2 to 3 inches. Their cost is generally not prohibitive compared to some of the higher-priced freshwater fish. They are not commercially bred, and a lot of the price comes from the cost of shipping from Africa. Congo River fishes are generally more commonly available in Europe. Occasionally one might find a larger specimen in a store that was traded in by a customer.

The booklet I had as a kid listed the size for these fish at 10 inches, but modern sources report their size to be anywhere from 14 to 40 inches. Early reports were certainly skewed by the premature deaths of specimens kept in aquaria that were too small.

Generally people purchase a 2- to 3-inch fish from the store and put it in a reasonably sized tank; something in the range of 75 gallons would be the minimum I’d recommend. The fish begins to grow at an alarming rate until it reaches a size of about 8 to 11 inches, at which point the growth rate slows substantially. At this size the color in the body will have faded a little, maybe taking on a slightly greenish sheen in the bars, and the tail will still be bright red. As I mentioned earlier, they will turn completely gray when they reach their full-grown size. Such change in color is not unusual for Distichodus spp.,as similar color changes for D. schenga and D. mossambicus (two species that are just about never seen in the hobby) have been observed.

I’ve only ever seen one D. sexfasciatus that had grown large enough to have turned completely gray. It was in a pet shop in a custom-built tank that probably held about 400 to 500 gallons. My first impression was that this can’t be the same fish, but the distinctive body shape confirmed its identity. The fish was completely gray with no hint of any bars. The gray was a dull, ugly gray, with no reflectivity or shine at all. The fish was somewhat larger than the big pacus that were in with it, and it was probably pretty close to 40 inches.

Feeding

So what do these fish eat? One of the clues to being able to tell what a fish eats is the proportional distance from the mouth to the anal fin. If the distance is long, it indicates a long digestive tract and that the fish probably has plant matter in its diet, since plants are more difficult to digest and require a longer digestive tract. D. sexfasciatus has a long digestive tract and is known to eat plant matter. It also eats worms and crustaceans, and its subterminal (under-the-snout) mouth indicates it is probably also a detritivore.

In the aquarium, I haven’t been able to find anything they won’t eat. They will greedily consume flakes, pellets, freeze-dried, and frozen foods. In nature they opportunistically eat fruits and seeds. I haven’t noticed that diet has much of an effect on their colors. I think that since they consume such a wide variety of foods, they will get what they need to maintain their color no matter what individual food items are added.

Since they are herbivores, many have been concerned about keeping them in a planted tank. I’m not very good with plants, so I generally don’t keep them in planted tanks, but I did it once with a tank that was set in front of a window. Because of the bright light from the window, the plants grew very quickly and I never noticed any plant damage from being nibbled by the fish. I never saw the D. sexfasciatus eating the plants, and if it did, the plant growth probably exceeded the destruction. I also think that the fish preferred the foods that were offered instead of the plants. Based on my experience, it is therefore possible to keep six-barred Distichodus in a planted tank, but it is a very risky thing to do.

Incidentally, that fish was about 12 inches long and was probably the most colorful one I’ve ever had. That may have had to do with the lighting and abundant cover, but it may also be taken as a contradiction of what I wrote previously about color and diet. I can’t be sure.

Behavior

What about behavior? The booklet I had said they were peaceful. Others have claimed that they were downright aggressive. Aggressive behavior has been documented and compared to cichlids (Baute and Poncin, 1993). When the little ones first show up in stores, they have a tendency to have some fin damage inflicted by fights among themselves that occur in holding tanks. In the wild they school together at this size. I’ve seen small ones trying to integrate into a school of clown loaches and, as they get bigger, start nipping at the clown loaches’ fins and later ignore them altogether. I had one once that hid from everything all the time, which was highly unusual, as they usually roam the tank in a very confident manner.

I believe a lot of the issues about aggression correlate to the size of the tank they are kept in—the bigger the tank, the less of a problem. In fact, I’ve never had an instance where a D. sexfasciatus did any more damage than a nipped fin or a few missing scales, but others report that they are real monsters. I’ve also never kept them in a tank smaller than 90 gallons.

As I was preparing this article, a friend asked me to take two large ones from him because their mere presence was interfering with the courtship of some Aristochromis christyi in the tank. These two fish are about 17 inches long and were showing some scale damage, presumably from the A. christyi. I put them in the same tank. Soon afterward, one of them started bullying the other and I had to move one to another tank. There is a much smaller D. sexfasciatus in that first tank, and that fish was completely ignored by the big bully fish.

There are a few things that can be inferred from this experience. One is that behavior is variable depending on tankmates in the aquarium. The presence of the A. christyi and their courtship may have interfered with the aggression of the D. sexfasciatus that later became a bully toward the other, making it possible to keep more than one in the same tank. While I now have a very large and a relatively small D. sexfasciatus in the same tank with no problems, I do not recommend keeping more than one per tank.

I’ve observed similar issues with large fish in that they may be aggressive toward each other and fish as large as themselves, but at the same time they are very tolerant of fish that are smaller than themselves. I’ve never lost a D. sexfasciatus due to aggression from tankmates, and they seem to be able to take care of themselves even among large, aggressive cichlids. Many aquarists have kept them in Rift Lake cichlid tanks, as demonstrated by my friend with the A. christyi.

Water Conditions

What about the water conditions in those cichlid tanks? D. sexfasciatus is found in Lake Tanganyika in the swampy drainage areas but never in the high-pH parts of the lake. It is more commonly known from the Congo River, which suggests the soft acidic water of the jungle stream. Experience shows that it is very tolerant of a wide range of water chemistry values, since it has been kept in the hard, alkaline water of the Rift Lake cichlids as well as soft, acidic waters. I don’t think there is a hard-and-fast rule for water conditions; if you’ve got other tropical fish thriving in your water, D. sexfasciatus should do well in that water too.

Spawning

Spawning has never been achieved in captivity and probably never will be due to the problems of size and compatibility. Although they school together as youngsters, they don’t get along in captivity, and they don’t get along well as adults. There is also the problem that, like other large characins, they probably go through some sort of migration before spawning that can’t be duplicated in captivity. Of course, with the work being done with hormone treatments, it is entirely possible that they will be commercially produced one day.

Space is Key

So should you acquire a D. sexfasciatus? I would say yes, but only if you have the tank space available now. I strongly discourage people from buying a fish that will outgrow their tank space with the idea that they are planning on getting a large tank later. Wait until you get that large tank, and make sure you have room in it for a fish that will grow to 3 feet or more. While D. sexfasciatus may have certain drawbacks as an aquarium fish, I find that the pros outweigh the cons. It is a beautiful fish that draws comments from even those who are not normally interested in fish.

Works Cited

Baute, P., and P. Poncin. 1993. “Preliminary study of the behaviour of Distichodus sexfasciatus Boulenger 1897 in aquarium: ethogram, social behaviour and daily rhythm of feeding activity.” Cahiers d'Ethologie Fondamentale et Appliquee, Animale et Humaine 12(4):509–518.

Stewart, K. 2001. “The freshwater fish of Neogene Africa (Miocene–Pleistocene): systematics and biogeography.” Fish and Fisheries 2(3):177–230.



See the full article on TFH Digital http://www.tfhdigital.com/tfh/201111#pg93

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