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Issue: April 2012

Breeding the Imperial Tetra (Full Article)

Author: Mike Hellweg

HELL T 0412
Photographer: Mike Hellweg

A relatively new addition to the hobby, the imperial tetra has proven to be a challenge to breed, but this master fish breeder has devised a sure method for spawning the species in captivity.

The heyday of tetras in the hobby was the 20-year period from the late 1940s through the late 1960s. Several books about tetras were published, and the fish were in high demand. New species were being imported on a weekly basis, and you could only find new species in the local fish store if you got there on the day the fish arrived, otherwise you risked missing out on having the latest and greatest. To stay ahead of this demand, several tropical fish importers even bought retired WWII aircraft from the US government and repurposed them into tropical fish transports that flew back and forth from South America, bringing new and interesting fish with each trip.

Aquarium magazines of the time, including TFH, regularly published breeding articles as hobbyists shared their successes. For tetra fans, these giddy times seemed to slow down in the next several decades, but in the past few years, this has been changing. Several stunning new tetras have been described by scientists, and many are also making their way around the aquarium hobby, with hobbyists creating demand by sharing pictures and trading them over the Internet even before they become established in the commercial trade. One of these beauties is Hyphessobrycon nigricinctus, which seems to have garnered the impressive-sounding common name of imperial tetra.

The imperial tetra (sometimes also labeled as the Morado tetra) was first found about 10 years ago in the Madre de Dios River in southern Peru. The wild habitat is marked by less rainfall and a lower high-water season than many other areas of the Amazon drainage, so the fish don’t experience as much seasonality in their habitat as some of their cousins in the other parts of the Amazon Basin do. This may have relevance in their captive breeding, as it appears they are not seasonal spawners in captivity.

The fishery east of Cuzco began to open to the aquarium hobby in 2002, and experts estimate there may be many more species in this area that are yet to be described. The imperial tetra was one of the first new fish from this area to enter the hobby. In 2004, it was also one of the first of these new fish to be described by science. It was given the name H. nigricinctus by Zarske and Géry. Around this time, it was also being imported in decent numbers and some hobbyists were starting to keep them. But the first spawning reports didn’t start appearing until about four years later.

Even today, they aren’t commonly kept, and only a few people have reported any luck with getting them to spawn. Hopefully that will change as more people begin to work with them and commercial breeders start to produce them in quantities. While I’ve found them to be undemanding and relatively easy to spawn once sexually mature, others have had very different experiences. If you have not yet tried spawning any tetras, I recommend trying a few of the easier species first to build up your confidence; otherwise, these guys might make you reconsider breeding tetras!

Captive Requirements

Aquarium care is straightforward as it is for most Hyphessobrycon species. Give them at least a 15- or 20-gallon tank, good filtration maintained according to the manufacturer’s instructions, some room to swim, and some plants around the edges to feel secure. They seem to be most happy with water temperatures in the middle to upper 70s. Large, regular water changes are in order.

It is a good idea to add driftwood and/or dried hardwood leaves to the tank. I use oak leaves, but others find similar success with beech, almond, and others. These slowly decay and add tannins and other beneficial substances to the water. They also add a slightly yellow or brownish tint to the water over time. Many breeders and keepers think this looks more natural and makes the colors of the fish pop, but some people do not like it and think all aquarium water should be crystal clear, even if it does not benefit the fish. To clear the water, run a filter with activated carbon, which will remove the tannin stains in just a few hours. If you want something that more closely resembles the natural habitat, light-colored fine sand would be in order. But to bring out the richest color in the fish, use a dark substrate.

All Hyphessobrycon species are schooling fish, and the imperial tetra is no exception. They like to be in decent-sized groups, so aim for a group of at least eight to twelve fish. They are peaceful fish and do well with other peaceful species, so keep them with cories, small Loricariids, other Hyphessobrycon or Hemigrammus species, pencilfish, hatchetfish, small barbs and rasboras, and even killies.

Feeding is not a problem. Even wild-caught fish will take high-quality flakes and pellets. Add live and frozen meaty foods several times a week. They will take frozen mysis, brine shrimp, bloodworms, daphnia, and similar foods. They will also take live baby brine shrimp (even the adults will eat this), Grindal worms, whiteworms, blackworms, daphnia, young cherry shrimp, young Gammarus shrimp, and similar foods. They do not seem to be as interested in things that stay near the surface, such as fruit flies and flour beetles. When conditioning for spawning, enhance their diet by adding chopped earthworms and minced shrimp from the grocery store for a week or so prior to setting them up.

Both males and females seem to reach a similar adult size of just over 1¼ inches or so standard length. Females are a bit stockier and a bit higher bodied. In addition, males have red edges on all of their unpaired fins, while those of females are colorless. They remind some visitors of my fishroom of black neon tetras (Hyphessobrycon herbertaxelrodi), but a closer look will reveal that they are not the same fish. The red-edged fins, red eye, red adipose fin, and wide, even, velvety black band extending into the center of the caudal fin—edged with a thin greenish-silver band above on a silver body—are dead giveaways. I’ve seen some photos online showing males with bright red tails, but I have not seen that in any of my specimens.

My Experiences with Imperial Tetras

First Try

I first came across the imperial tetra about five years ago at one of the local shops I visited while on a speaking trip. Even though they were a bit expensive, I picked up three pairs. Unfortunately, two of the females did not survive the trip home because my luggage was lost by the airline and spent an extra day in transit. I acclimated the remaining fish with great care in a quarantine tank, and they settled in quickly and showed no sign of disease.

Over the next several months, they finished growing out. I set them up for a spawn for the first time in late summer, about six months after I acquired them. I treated them like most other Hyphessobrycon species, separating the female for a week, conditioning both her and the male on lots of meaty foods as described above, and putting them together one evening just before lights out. I used a 5-gallon tank with a pile of bottom acrylic spawning mops and a couple of floating mops.

By the time I checked on them the next morning, they were done spawning, so I removed the adults. Unfortunately, all of the eggs had fungused by the following morning. While disappointed, I was not ready to give up. It could be that things were just a bit too warm, as it was August and the ambient temperature in the fishroom was around 80°F. I waited a few more months and, as I got ready to try again, something happened to the lone remaining female, which I found dead in the tank.

Second Attempt

It would be almost two years before I found more fish. By that time, Ted Judy and I were in the midst of the “TFH Breeder’s Challenge,” and I put the group of a dozen juveniles in a 30-gallon breeder with an assorted group of various tetras for grow out and pretty much ignored them. I eventually worked my way through the other species in the tank, and the imperial tetras reached sexual maturity.

I separated the males and females and conditioned them on live blackworms, chopped earthworms, and minced shrimp. After about two weeks, I set up a couple of spawning tanks, one with a pair and one with a group to see which would work better. The pair went into a 5-gallon tank, and the group went into a 10-gallon tank. Both were set up with a pile of mops on the bottom and a couple of hanging mops. The water was about 76° with a pH of 6.8 and a total hardness of about 60 ppm. Carbonates (alkalinity) were almost immeasurable. This seems to be a quirk of our local tap water this past year. Our water comes from the Missouri River, which has been at or near flood stage for most of the year due to massive snow melt up near the headwaters. All of this has produced water that has dogged the Malawi cichlid enthusiasts, as they have needed to add all kinds of products to harden and buffer the water, but for characin enthusiasts, this soft, low-carbonate water has been like liquid gold.

The pair spawned overnight and was removed first thing in the morning. The group dynamics in the other tank apparently meant either the males spent all of their time posturing and displaying for one another or the nonbreeding fish consumed the eggs as soon as they were laid. As it turned out, a few fry did show up in this group tank, but this was nothing like the results for the pair. This time, the eggs from the pair appeared to be nearly completely fertile. A few days later, I was rewarded with a cloud of fry darting around the pair tank. I was also surprised to find a dozen or so fry in the group tank.

Raising the Fry

I started the fry on my soup mix: infusoria, green water, and microworms fed on a drip line into the tank. This supplies the fry with live food all day long and gives them many different critters from which to choose when they are hunting, just like they would encounter in the wild. I’ve found the best growth with using this method, especially with new species when no one is really sure what the fry will eat. Just be sure there is enough room in the fry tank for all of the water. I find it’s a good excuse to do a small daily water change with a piece of airline tubing.

By the third day of feeding the soup mix, I added some newly hatched brine shrimp nauplii. Within about 20 minutes, I could tell the young fish were eating the brine shrimp, so at the next feeding, I changed the soup mix to newly hatched brine shrimp and microworms. They received this food twice a day instead of via drip method. I continued doing water changes every other day for the next week and then switched to every third day. By the end of the third week, they were starting to look like miniature copies of the adults, and by seven weeks, many were nearly ¾ inch long.

At this time, I moved the young fish into a 10-gallon tank with a wall-type sponge filter and switched them to once-weekly water changes like the adults. I also started mixing in finely ground high-quality flakes at feeding time. By the end of their third month, they were eating almost entirely flake food with just occasional feeds of meaty foods, just like the adults. They were now growing quickly, so I had to spread them out into a couple of 30-gallon grow-out tanks to avoid stunting them. They were also now large enough that it was time for me to find homes for them. I found them to be in high demand among other characin aficionados.

A Special Surprise

While I was doing all of this hard work giving the fry all kinds of special care, the adults were merrily going about their business in their home tank, a 30-gallon breeder. I allowed Java moss to grow and fill about two thirds of the adults’ tank. While doing a water change, I decided it was time to thin out this crop of Java moss. I was surprised to discover dozens of little 3/8- to ½-inch-long fry hiding among the Java moss!

I had done nothing special in this tank. I immediately tested the water: The temperature was 74°, pH was 6.8, the total hardness was about 60 ppm, and carbonates were barely measurable. I had not given the tank any special feeding for the fry, so they were subsisting on the microfauna living on and around the Java moss, which was also providing them with a hiding place from the adults. The young fish spent most of their time low in the water column, hiding under this mound of Java moss. Once I started adding newly hatched brine shrimp and microworms to this tank as well, I found more and more young fish coming out of the shadows. Once they reached about a ½ inch in size, they moved higher in the water column and joined the adult group.

I have not noticed any damaged fins, nor have I found any dead young fish, so I’m guessing they are all getting along pretty well. I should note that this tank has no other fish species other than a lone Epiplatys killifish that hatched and grew up in that tank, and I don’t have any snails in this particular tank either. After all that hard work, all I had to do was feed them and leave them alone!

If you come across any of the new tetras, don’t hesitate to give them a try. Even if you don’t have luck getting them to spawn, you still will enjoy their fascinating behavior and their elegant beauty, harkening back to a day in the hobby when tetras were all the rage.



See the full article on TFH Digital http://www.tfhdigital.com/tfh/201204#pg67

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