Dwarf Puffers Are Great Little Freshwater Fish

Dwarf puffers are cute, intelligent, watchful and clearly aware of what is going on outside of the aquarium.

The Dwarf Puffer (Carinotetraodon travancoricus) is the only known freshwater pufferfish. Via Lindy de Bruyn/Flickr

Puffers are cute. There’s no other way to put it. They are intelligent, watchful and clearly aware of what is going on outside of the aquarium. They watch us as much as we watch them. They ensnare unsuspecting hobbyists with the way they interact with people on the other side of the glass, following their movements, most likely hoping for fish food. Their “act” is almost irresistible. Their cherubic faces add to the attraction. They move deliberately with their clear pectoral fins, appearing to glide through the water. Their huge tails are used both like a boat’s rudder to steer gracefully and effortlessly through the water, and like a brake to stop and inspect any potential food morsel. Finally, their ability to inflate with water or air when frightened is just plain amazing.

Only when the hobbyist brings one or more home to plunk into the community aquarium does the cute puffer show its true colors, becoming an aquatic “Dr. Jekyll and Mr. Hyde.” Within a day or two, every other fish in the aquarium has chunks bitten out of its fins, or has been eaten, if the puffer is large enough. If there were two puffers to start with, now there is only one. And the puffer is miserable because it’s not really a true freshwater fish but rather needs quite a bit of salt in the water to be happy. This is the way it has been for most of the time I have been in the hobby — but not anymore!

Create a cool pufferfish pad

A few years ago, exporters in India began shipping more of their native fish to the United States and Europe. Among those fish were a few relatively obscure little puffers about the size of a pea (hence one of their trade names). For a while, most people assumed that these were juveniles of one of the common puffers in the trade–but they never grew any larger. Within a year or so, we knew that we were dealing with a new type of puffer. This importation has opened the door to a group of totally freshwater, small, colorful, interesting and relatively peaceful little puffers: the members of the genus Carinotetraodon. Not only are they interesting and peaceful, you can keep them in groups, and keep the groups with other fish without many problems.

The most available member of the genus is the pygmy or dwarf puffer (Carinotetraodon travancoricus), also sometimes called the pea puffer. A fully grown adult male will top out at about three-fourths of an inch (about 2.2 centimeters). Males exhibit deep green coloration often highlighted with gold, and a golden to orange belly. Females are a bit plain, with lighter colors, no golden highlights and a whitish belly.

These diminutive blowfish come from Kerala State in Southwestern India and are collected in the River Pamba. They are not picky about water conditions and will adjust to most local water supplies without trouble. They are ravenous eaters, consuming just about any live or frozen food. Unlike many larger puffer species, they don’t seem to enjoy frozen mussel and will just pick at it, while their larger cousins will gulp it down whole. They will even eat flake and pellet foods, though they don’t seem to respond as well to them and will slowly waste away if that is all you feed them. Their particular favorites are frozen bloodworms, other worms of any kind and newly hatched brine shrimp. They love snails and will quickly depopulate an aquarium of these sometimes annoying gastropods.

A 20-gallon aquarium is perfect for a group of these cute little guys. I’ve kept a group of 14 adults in a planted 20 long for more than a year with no problems. I’ve also kept them with other species in larger community aquariums and can only report the occasional nipped extension on some slow-moving fishes’ fins. Other hobbyists have also reported the occasional nipped fin. Beyond that, they are model residents.

As I mentioned earlier, water parameters don’t seem too important. I’ve kept and spawned my fish in my local tap water, with pH 7.2 and total hardness about 125 ppm (with about 60 to 70 ppm of that being carbonate hardness). Water temperatures in my fish room are in the mid-70s, and I do regular water changes of about 50 percent every week. Their home aquariums are always well planted with crypts, Java fern, smaller swords and other plants. This seems to be to their liking – they are always out in the open, watching me when I work in the fish room.

They have an interesting social structure when kept in a group. They school loosely, with the males taking up residence at the base of plants throughout the aquarium. They seem to perform a greeting ritual when moving into one another’s territory. It almost looks like they are bowing to one another, with the “invading” fish initiating the ritual. Nipped fins are rare, and I’ve never had one fish seriously injure or kill another, as is often the case with their larger cousins. There are few fights, though you will see an occasional chase throughout the aquarium. It’s amazing how fast they can swim when they need to!

I worked for several years to get my first spawn. I tried everything: changing the water pH, salinity, hardness, temperature; doing no water changes for a month or more, then doing several large water changes to simulate the onset of the rainy season; changing foods, etc. I tried a group setup, then pairs and trios. Nothing worked. I read every article I could find. Most dealt with larger brackish water species and mentioned that they were usually substrate spawners, with the male puffer guarding the eggs and fry like cichlid fish females. I tried sand, gravel and bare-bottom aquariums. Still, nothing worked. I could see that the females were full of eggs, and the males were colored up and it almost looked like I was watching courting behavior–but I never found any eggs. Finally, in frustration, I gave up.

I moved the group to a 10-gallon planted aquarium with a large clump of Java moss attached to some rocks in the center of the aquarium. The next morning, when I was going to feed the fish, I noticed a lot of whitish things in the Java moss – about 100 or so eggs. I realized I had done everything but provide them with the spawning substrate they wanted. It turns out that they are egg-scatterers and require a clump of mosslike plants upon which to scatter their eggs. Perhaps they use an aquatic moss or an algae mat in the wild. Further reading has confirmed that this is indeed the preferred spawning method for the entire genus Carinotetraodon (at least the species that have been spawned to date).

The eggs take four to five days to hatch, depending on temperature. The fry are like tiny tadpoles, appearing to be little more than the egg itself with eyes, a tail and tiny fins. They start eating about one week after they hatch and require tiny foods like infusoria, commercial liquid fry foods or frozen cyclops for several more days. I started adding newly hatched brine shrimp at about 10 days after the hatch, and all of the fry were eating it. I continued with the frozen cyclops, along with daily feeds of newly hatched brine shrimp. In addition, as with all fry aquariums, I kept Java moss in the aquarium to provide a source of microfauna for the fry to graze upon all day. The fry and juveniles school loosely, scattering all over the aquarium and only coming together to feed. They grow quickly and are three-eighths to one-half an inch at about 5 weeks old.

The next time you come across these cute little guys in your dealer’s aquariums, don’t be afraid to give them a try. They aren’t anything like the larger puffers that are more familiar to most hobbyists and shop owners. For their size, they have a lot of  “personality” and are everything that a fishkeeper is looking for in a fish.

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Fish · Freshwater Fish