The Dwarf Puffer: A Pleasant Little Surprise

Author: Mike Hellweg

With a perfect mix of charm, intelligence, and spunk, the dwarf puffers from India's Pamba River are fascinating creatures to keep—and breed—in the home aquarium.

The New Aquarium Staple

In the last 12 years or so the aquarium hobby has seen an explosion of new fishes from India. Several of them—the torpedo-shaped redline barb Puntius denisonii, the stunning drapefin barb Oreichthys sp., the beautiful scarlet badis Dario dario, and many others—have even become new staples of the industry. Out of all of these fishes from India, one that attracts the most interest from hobbyists is the dwarf puffer Carinotetraodon travancoricus.

Coming to the hobby from a land that is steeped in ancient and exotic mystery, where even the locality names evoke the mystique of the old world, these diminutive blowfish take their name from the old Maharaja-ruled Indian principality that was known as Travancore. It is located in the present-day Indian state of Kerala, on the western coast of southern India. This beautiful land far to the south of the city of Mumbai (formerly called Bombay) is crisscrossed with rivers and is the home to many long-time popular aquarium fish, such as the spiketail paradise fish Pseudosphromenus dayi, the glass perch or glassfish Parambassis ranga (formerly Chanda ranga), and the giant danio Devario malabaricus.

It should be noted that dwarf puffers make their home in the Pamba River, which flows from the mountains of the Western Ghats into the Vembanad Lake (another location these fish have been collected). This means that these fish, unlike many of their more well-known puffer cousins, are purely freshwater fish and do not appreciate the addition of salt to their water.

Aquarium Setup

In captivity, they are not too picky about water parameters. As long as extremes are avoided, your fish should do just fine. Spawns have been reported by many hobbyists in both hard and soft water with a recorded pH both slightly above and slightly below neutral. I have kept and bred them in water with a neutral to slightly basic pH, a total hardness around 125 ppm (with about half of that coming from carbonates), and a temperature in the mid to upper 70s (F).

It does appear that clean water is important. Keep the dissolved organics and nitrates low by doing large regular water changes, especially if you are keeping them in smaller tanks. If you provide them with clean water and the right foods, dwarf puffers will reward you with many years of unique behavior.

These fish prefer well-planted tanks with some areas where each male can set up his territory. They do well in smaller tanks, and a pair or trio can be kept in a desktop tank. A good filter helps maintain water quality, but make sure the flow isn’t too strong. Puffers in general are not strong swimmers and seem to prefer areas with lesser water flow. I use sponge filters in my tanks where I can adjust the flow from practically nothing to a raging torrent. For the puffers, I keep the flow at a fairly slow rate.

Aggression

Most of the dwarfs that I’ve kept have been pretty easygoing (other than the occasional territorial display or fin nip), but other aquarists have reported incidents of aggression. According to these reports, males especially can be quite nasty toward their conspecifics. If a fish is injured, it is a good idea to move it to a separate tank for treatment, as the other fish will begin picking at its wound until the injured fish dies. While certain individual dwarfs can show these aggressive tendencies, in my experience aggressive dwarf puffers are not common.

C. travancoricus can be kept in community tanks with small fish. I have read several accounts where they have nipped the fins of slow-swimming fish, so keep that in mind when choosing tankmates. I have not witnessed anything more than an occasional nipped fin among their tankmates, except when there is a spawn. Even so, I prefer to keep them in a tank by themselves just so I can watch their unique behavior. In my experience I have found dwarf puffers to be hardy, peaceful once settled in, and long lived. I have enjoyed keeping at least a small group of them for most of the past decade.

“Poison” and Puffers

The Internet can be a wonderful thing. It is also unfortunately the source of many half-truths, urban legends, and downright falsehoods that are spread as fact. Unfortunately, the dwarf puffer seems to be suffering from a bit of that right now. Every time I give a talk to a club and I mention working with the dwarfs, I have at least one person come up to me afterwards to if I’m aware of the dangers of keeping these “poisonous” fish. Many people seem to confuse “poisonous” with “venomous,” and it’s clear from talking to some hobbyists that this is the case with these tiny puffers.

Toxins

As you might know from murder mysteries and crime dramas on television, some puffer species are known to have a sometimes-deadly toxin in their bodies. Of course there is the Japanese dish fugu that may only be prepared by a specially trained and licensed chef. The small amount of this toxin in the flesh of these blowfish causes a pleasurable tingling or numbness in the lips and mouth and a slight “high” when it is consumed. Eating certain organs where the majority of the toxin resides, however, can cause death.

It is important for hobbyists to note that this toxin is only produced in some species of blowfish, and it is entirely diet related. Levels of the toxin fluctuate throughout the year based on the availability of the food items that are the source. Synthesis of the toxin requires both a certain bacteria and a certain type of algae that grows on the shells of certain mollusks. Both must be ingested in quantity by the puffer in question. If either of these items is absent from the diet, no toxin is produced.

In marine (and some brackish) species, this toxin is called tetrodotoxin. It accumulates mainly in the organs, with only a small amount accumulating in the flesh. In freshwater species, this toxin is called saxitoxin and it accumulates in the flesh. Eating the flesh of these freshwater fish can cause (and has caused) death, hence the source of the rumors.

Without the dietary sources, the toxin in wild-caught puffers dissipates with time, as evidenced by the seasonal fluctuations. Though I have found much hobbyist-based speculation (often stated as fact) on the Internet, I have found no scientific evidence to support the idea that C. travancoricus ever, even in the wild, synthesizes saxitoxin. That is not to say they don’t, just that I have not seen any scientific evidence that they do; the only freshwater puffer species I have found in the literature associated with saxitoxin is Tetraodon cutcutia.

Snails

Dwarfs in captivity do eat small snails. Small snails are generally very young and haven’t had time for any algae to accumulate on their shells. On the rare occasions when dwarf puffers in captivity do eat larger snails, they usually eat only the flesh and not the shell. So it’s not likely that they ever ingest enough of the necessary algae in the wild—if it is even found in their habitat—to synthesize this toxin.

How Diet Affects Toxins

It all boils down to the simple fact that captive-raised puffers do not produce the toxin if they are not exposed to these specific bacteria and algae in their diet. There is nothing for the hobbyist to fear; even if the toxin is found in wild-caught dwarfs, it can’t harm you unless you eat the fish!

In my research for this article I’ve read anecdotal evidence (again, on the Internet, so consider the source) stating that larger fish that have consumed dwarfs have died soon thereafter. Whether this is a result of poisoning or of the little fish inflating itself and getting stuck in the larger fish’s digestive tract is never noted. I was unable to find a single instance where either a necropsy or any toxicology screening was done to verify the cause of the larger fish’s death. To be safe for both the puffers and for larger fish, I would not recommend keeping the dwarfs with any fish that can swallow them. But then again, no small fish should be kept with tankmates that can swallow them.

The Name Game

Like many other fish, Carinotetraodon travancoricus is known by a few different common names. I first encountered them at a local wholesaler in 1996 under the trade name pea puffer. The name fit, as they are not much larger than a pea when they are offered for sale. Many in the trade still call them by that name. I’ve also seen them variously listed as dwarf puffers, pygmy puffers, red green dwarf puffers (I’m not really sure how that one applies), gold green dwarf puffers, blue line puffers, and Malabar puffers. I’ve seen them attached to the scientific names of Tetraodon travancoricus (they were described under this name in 1941), Monotretus travancoricus, and Carinotetraodon travancoricus. The latter is currently considered correct. I really like the common name of dwarf puffer, so that is the one I use.

As with many miniature fishes, their scientific name is larger than the fish itself—really big males barely reach ¾ of an inch, and the females are just a bit smaller.

Sexing

As adults, C. travancoricus are easily sexed. As you can see in the accompanying photos, males have a deep golden belly with a black line or ridge running from just under the head to the caudal peduncle. Males also have dark bluish or even black long ovals and stripes on their backs and sides. In females and juveniles, these dark markings are smaller spots. Females also have a white belly, sometimes with a golden patch on the throat.

Intelligent Fish

Puffers are known for their intelligence, their curiosity, and their awareness of what is going on outside of their tank. Dwarfs are no exception. They carefully and deliberately search every surface in their tank and pay close attention to activity elsewhere in the room, as well. They beg for food whenever their owner is close by, moving up and down the glass and spending more time at the area where they are usually fed. If you are not careful, it’s pretty easy to overfeed your puffers.

Feeding

Dwarf puffers should have a varied diet. I feed mine daily with an assortment of live foods like newly hatched brine shrimp, grindal worms, and occasionally larger worms like blackworms and whiteworms. They enjoy Daphnia and Moina, and they are able to eat adult brine shrimp if it is offered. I’ve seen them go after Gammarus, but I’ve neither seen them catch nor eat any. I also add ramshorn snails to their tank. They don’t seem too interested in adult snails, but they will eat tiny young ramshorns.

For those who do not want to deal with live foods, some hobbyists do report that dwarf puffers will take flake and pellets as a staple diet, but of the dozens of these fish that I’ve kept, I have only been able to get a few of them to take those types of prepared foods. They seem to be more likely to take these types of foods in a community situation where they see other fish enjoying their meal. But there is good news—they will eat frozen and freeze-dried bloodworms, as well as finely ground frozen and freeze dried krill and brine shrimp. Many individuals will also take finely shredded frozen mussels. Before feeding any freeze-dried foods it is a good idea to re-hydrate them by soaking them in water for 20 minutes or so. They can then be fed to the fish by baster or pipette, or even just poured directly into the tank.

By providing my dwarf puffers a mixed diet and some tiny snails to munch upon, I haven’t experienced trouble with any individual’s teeth growing too large that they would need a trim, as sometimes occurs with larger freshwater puffers. That’s a good thing, too, as I have no idea how I would perform this type of delicate dentistry on their tiny mouths.

A First Attempt at Spawning

In late 1996, after seeing them for the better part of a year every time I visited our local wholesaler, I finally decided to try a group of dwarf puffers. There was almost no information available about these unique little fish, so over the next few years I tried various setups to try and find what they required. Our local wholesaler couldn’t tell me much more than that they were from India and did not grow very big. He also thought they were freshwater fish, though he kept them in the brackish system with the larger puffers, gobies, mudskippers, and archerfish. They survived, but did not thrive in that setup. Nevertheless, the wholesaler never put them into a freshwater system.

Bring It On

At first I tried to research them, but “pea puffers” were not mentioned in any books available in English at the time. I also could not find any mention of them in my collection of magazines. While some folks were on the primitive Internet of the day, it would be another four years before I even considered the purchase of a computer. I even tried a search of the local university libraries without success. So I was on my own, but definitely up for the challenge. None of my friends from the local club were able to guide me, nor were any of my far-flung hobbyist friends from what was then known as the North American Fish Breeder’s Guild.

All of the hobbyists I spoke with thought dwarf puffers should be a brackish fish because “all puffers are brackish-water or marine fish.” I knew of at least one puffer from South America that was a pure freshwater fish, and armed with that knowledge and the limited information I could get from my wholesaler, I bought a group of 25 of them. They were tiny, barely the size of a pea, at about 3/8 of an inch long. A fellow local aquarium club member who had kept larger puffers many times over the years wanted to try them too, so we split up the group. I wound up with 14 fish, and he kept a baker’s dozen. It pays to be a regular customer of a locally owned business, as sometimes they add a few extras for their good customers!

Tank Setup

I set mine up in a pure freshwater, planted 20-gallon long, and my friend tried his in a brackish setup in a 29-gallon tank. I fed a mixed live food diet, and after accidentally discovering they also liked frozen bloodworms, I started adding those as well. My friend tried a diet of small apple snails Pomacea sp. and shredded mussels, as that is what his larger puffers ate.

After about a month, he called me and offered me his survivors. He dropped off his three very skinny fish a few days later, and after a brief quarantine and fattening up period, I added them to my group. I had not realized how much size my fish had put on in just a few weeks time. The established group was nearly double the size of the new fish and immediately began harassing them, so I had to pull the new ones out. I never was able to integrate those three fish into my group, so eventually I passed them along to another hobbyist.

The tank was set up with a large stand of Cryptocoryne wendtii that had spread to take over most of the tank. Eventually the dwarfs grew and reached what turned out to be their adult size of about ¾ inch. The individual males stopped swimming with the school and started hanging around their own individual territories until the remaining school was all females. The six males had each claimed their own little corner of the world at the base of the plant stands. Other than a little nipping and the occasional torn fin, there was little in the way of interaction between the males except at feeding time, when all territories were temporarily forgotten. After a meal, there was a bit of chaos as they all began to realize that “hey, you’re in my space.” But this would settle back down pretty quickly, only to be repeated again at the next feeding time.

Schooling

The females schooled loosely, and interacted with each individual male as they moved through his territory. They went through a surprisingly complex dance of bows and displays, with the females initiating the bowing and the males seemingly trying to impress the females with their size, which was exaggerated by the stripe along the ridge of their belly. The setup was working and the little puffers were thriving, but they did not spawn.

Further Research

Over the next few years as the group thrived I started researching further. I found a few articles in old issues of TFH on breeding brackish-water puffers, so I tried a few of the different things that were suggested. I also tried to be creative, using things I’d done before for other small fish. I tried giving them an area of open sand, thickets of plants, and even some caves; I attempted to add plants with large crowns so the males could better mark their territory; I divided territories with driftwood or rocks; and I even tried grouping them differently—in pairs, trios, and two pairs. I tried combinations of these things with hard water, soft water, peat-filtered water, brackish water, and, thinking they might move downstream to the sea to spawn, even salt water. While they tolerated it, adding salt water was a bad idea and they didn’t like it at all. They refused to eat, and did little but hang near the bottom of the tank.

Nothing worked; over the next few years they continued to thrive but did not breed. I gave away small groups of them, hoping someone else might have better luck. No one did. Eventually, after about five years they began to die off—likely from reaching old age.

Success (or Dumb Luck) at Last!

Eventually I lost the last of my original group, but I decided to try again. The next time I saw them for sale, I bought a batch of three males and three females. They were a bit larger, nearly ¾ of an inch long and easily sexable. I set them up in a planted tank much like before. Also, thanks to the book Ornamental Aquarium Fish of India (T.F.H. Publications, 1999), I now knew that they came from India, they were a dwarf species, and their scientific name was Monotretus travancoricus. This was the first written record of the species that I was able to find; unfortunately, there was still no information about spawning them.

A Year of Frustration

Again I tried several different things from my bag of tricks to get them to spawn, working with this new group for nearly a year. I had no more success with this group. I could tell the females were full of eggs, but for some reason I was missing something. I tried large water changes right before a storm front came through. I tried going with no water changes for a long period of time, which turned out to be another bad idea, as they all got stressed out and one of the males died. I still had no luck. Finally in frustration I gave up.

In the Breeding Tank

I moved the surviving group of two males and three females out of the “breeding tank” because I had other fish that were ready to spawn and I needed the tank. Our club had an auction coming up in a couple of weeks, so I decided I would sell the dwarf puffers in the auction. I put them into a temporary holding tank, a 10-gallon loaded with Java moss attached to some small pieces of lava rock and filled with plain, dechlorinated tap water with a sponge filter. There were several other fish that would be going to the auction in that tank, too.

The next morning, all of the other fish were pretty chewed up. The largest male was driving all of the other fish away from a corner of the tank. The smaller male was all chewed up around his belly. The larger male wasn’t guarding a specific area, but rather the whole corner. I looked but didn’t see anything. While feeding the fish I noted that he stayed in the corner, and that all of the females looked markedly thinner. Hmmm…

Eureka!

I took a piece of tubing and moved the Java moss around a bit in “his” corner. There they were, down in the Java moss, a clump of creamy whitish eggs! There were easily 80 or more eggs in the “nest.” Success at last! I had been providing them with everything except the substrate they needed for laying their eggs. Later I learned that in the wild they spawn on mats of algae or moss.

I decided to move all of the fish out of that tank and leave the eggs where they were. Over the next few days, some of the eggs turned a brownish color, and most remained white. I removed the white eggs with a small baster, and by day four I could clearly see eyes in the remaining eggs. A little over 110 hours after I found them, the eggs hatched. The little tadpole-shaped larvae bounced around on the bottom when I moved the Java moss, so I let them be for a couple of days. They were tiny, probably less than 1/8 of an inch long. They looked basically like an egg with fins and a tiny tail. Since they were not yet swimming on their own, I assumed they would be using the rest of the contents of their yolk sac over the next few days.

Raising the Fry

I checked daily, and on the fifth day after hatching, I noted that some were starting to try and swim, so I added a slow dripping “cocktail” of green water, paramecia, and infusoria to their tank, and mixed in some vinegar eels. They did not appear to be chasing down the food for the first two days, so I also added some ramshorn snails to clean up any uneaten food that died. I also put in some Moina to help keep the water clear and provide the tiny puffers with young for them to hopefully eat. I continued this micro-food “cocktail” drip for 10 days, adding newly hatched brine shrimp and microworms to the mix after a week. When it was clear by the color of their bellies that all of the puffer fry were eating the newly hatched brine shrimp, I discontinued the smaller foods.

With egglayers, once the fry are feeding on newly hatched brine shrimp, you are usually over the hump and it’s just a matter of giving them clean water, room to grow, and lots of good quality food. The baby puffers are no different, and they grow quickly, reaching a saleable size of about ½ inch in just about two months.

I always leave a clump of Java moss in fry tanks since it is usually covered with all kinds of microfauna that serves for “between meal” snacks for the fry. The young dwarfs seemed to enjoy this snack as much as most other fry do.

Sharing the Wealth

I was able to raise 38 fry from this first attempt. It appears this is extremely abnormal, at least in my experience. Subsequent spawns have been much smaller. I’ve chalked it up to having three females spawn with the same male within a few hours, after not being able to spawn for months. I’m guessing this first spawn was so large due to the fact that the females were loaded with eggs, they were more than ready to spawn, and I finally provided them with a spawning substrate they found acceptable.

I passed out many pairs from this spawn (including the pair in the photos accompanying this article), and a couple of friends had some luck getting these first-generation fish to spawn. I have even been able to raise a second and a third generation from these cute little guys. Average spawns have been about seven, with many only producing two or three fry. One friend has even reported a single tiny puffer appearing in his well-planted tank, without his doing anything other than providing the adults with the proper food and a clump of Java moss to spawn on.

If you are looking for something a bit out of the ordinary, but that you would have a reasonable chance of success with spawning, you might want to consider the dwarf puffer. These amazing little fish are just the right mix of fishy charm, intelligence, and spunk that could be the perfect addition to your fish collection.

References

Ebert, Klaus. 2001. The Puffers of Fresh and Brackish Waters. Aqualog Verlag, Morfelden-Walldorf, Germany.

Tekriwal, Kishori Lal and Andrew Arunava Rao. 1999. Ornamental Aquarium Fish of India. T.F.H. Publications, Waterlooville, England.

Coates, Christopher and James W. Atz. 1954. Fishes of the World. Greystone Press, New York, NY.

Cousteau, Jacques Yves. 1985. Jacques Cousteau: The Ocean World. Harry N. Abrams Publishing, New York, NY.

Schultz, Leonard P. 1971. The Ways of Fishes. T.F.H. Publications, Neptune City, NJ.

Moyle, Peter B. 1993. Fish, an Enthusiast’s Guide. University of California Press, Berkeley and Los Angeles, CA.

Helfman, Gene S., Bruce B. Collette, and Douglas E. Facey. 1997. The Diversity of Fishes. Blackwell Science Inc., Malden, MA.