Licorice Gourami: Care, Habitat, and Species Insights

Soft, acidic blackwater streams across Malaysia, Indonesia, and southern Thailand shelter a small, dusky labyrinth fish in the genus Parosphromenus, family Osphronemidae. Adults reach only 3 to 6 cm, yet males flash iridescent blue, red, or green fin edges during display that rival any cichlid in visual punch. Caring for them demands a fundamentally different approach from typical community tanks, because their survival depends on replicating vanishing peat-swamp conditions that most aquarists never see.

This guide covers everything an aspiring keeper needs to bring home licorice gouramis successfully, from decoding the roughly 20 known Parosphromenus species to brewing tannin-rich water that triggers spawning in a home biotope.

A Small Fish From Southeast Asia’s Vanishing Blackwaters

The genus Parosphromenus sits inside the broader anabantiform group of labyrinth fish, the same order that contains bettas and gouramis you may already know. Roughly 20 recognized species are scattered across Peninsular Malaysia, Sumatra, Borneo, and southern Thailand, each tied to a specific river system or peat dome. Many were formally described only in the last two decades, and field researchers continue to find undescribed populations in remote swamp forest.

Natural habitat centers on peat swamps and forest streams stained the color of strong tea by tannins leaching from fallen leaves and submerged wood. In these waters, pH often drops below 5.0 and general hardness is nearly undetectable, sometimes measured at less than 1 °dGH. Light barely reaches the surface because overhanging trees and floating vegetation block most of it, so the fish have evolved to navigate by lateral line and chemical cues rather than sight.

The common name has nothing to do with the licorice plant. It refers to the slender, elongated body shape and the deep, dusky brown to charcoal coloration that males show outside of breeding display. Adults of most species stay between 3 and 6 cm, placing them firmly in the nano-fish category. That tiny adult size shapes every aspect of their captive care, from tank volume to food size to the mesh of any net you use.

Why the Habitat Matters for Captive Care

Blackwater fish evolved under chemical conditions that most municipal tap water cannot match. Trying to keep them in neutral pH with measurable hardness usually ends in slow decline, faded color, and immune collapse within months. Replicating the peat swamp is not optional; it is the foundation that every other care decision rests on.

Habitat loss has also turned this genus into a conservation priority. Logging, palm oil expansion, and peat drainage for agriculture are the primary drivers of population declines, and most species are now listed on the IUCN Red List as Endangered or Critically Endangered. Many fall under CITES Appendix II, which means international trade requires documented proof of legal origin. Healthy captive populations in home aquariums now serve as living insurance against total wild extinction.

Distinguishing the Species and Telling Males From Females

Coloration is the most reliable field clue. Males flare brilliant iridescent blue, red, or green fin edges during display, while females stay muted brown or gray with shorter, rounded dorsal fins. Outside of breeding, males often show a thin iridescent stripe along the dorsal edge that females lack entirely.

Several species, including P. deissneri, P. filamentosus, and P. quindecim, have been formally described only since the early 2000s, and confusion among wild-type populations remains common in the trade. Body shape and fin ray counts help separate closely related species, but location data from the importer or breeder is often the most practical identifier when taxonomy gets murky.

Sexing Juveniles and Mixed Groups

Juveniles of nearly every species look almost identical: pale brown bodies, clear fins, no iridescence. Sexing them with any confidence usually requires waiting until males begin to color up at sexual maturity, which can take 6 to 10 months depending on temperature and feeding. Rushing the process leads to mismatched pairs and frustrated breeders.

Resources like SeriouslyFish and the Parosphromenus Project maintain updated species pages with location data, male display photos, and known distribution. Cross-referencing a specimen’s photo against those references saves years of guesswork, especially for the more cryptic members of the genus like Parosphromenus linkei, which show subtle blue-green edging rather than the bold red bands seen in P. deissneri.

Common Species	Origin	Male Display Color	Distinguishing Trait
P. deissneri	Sumatra, Bangka	Red and blue bands	Long caudal filaments in dominant males
P. filamentosus	West Kalimantan	Blue-green with red edges	Extended middle caudal rays
P. linkei	Sumatra	Turquoise with black bands	Compact body, high dorsal
P. quindecim	Central Kalimantan	Red-orange caudal	15 soft dorsal rays, namesake trait

Building a Blackwater Tank That Mimics Their Native Streams

Target water parameters of pH 4.0 to 6.0, near-zero general hardness, and temperatures between 23 and 28 °C set the baseline. Matching those numbers consistently is what separates thriving colonies from fish that slowly fade over six months.

Use peat-filtered water, Indian almond leaves, alder cones, or pre-conditioned RO water to release humic acids and lower pH gradually. Sudden drops stress the fish far more than stable conditions at the high end of their tolerance range. Aim to change parameters by no more than 0.2 pH units per week when conditioning a new setup.

Substrate, Plants, and Light

Choose dim lighting, dense plant cover including Cryptocoryne species and floating Salvinia, and a dark substrate of fine sand or aged leaf litter. The dark base absorbs stray light and makes the males’ iridescent colors pop during display, which also encourages natural courtship behavior.

Keep filtration gentle with sponge filters or baffled outputs, since these fish originate from slow-moving or still sections of forest waterways. A 30-liter species tank suits a single pair; a 60-liter tank supports a male with two or three females comfortably. Larger setups work for groups but need broken sight lines with driftwood and leaf piles to prevent male-on-male aggression.

“Aged ketapang leaves do more than tint the water. They release antimicrobial tannins that suppress opportunistic infections, buffer pH swings, and host infusoria that fry graze on during their first days of life.

Feeding, Tankmates, and Day-to-Day Maintenance

Diet leans heavily on small live and frozen foods such as microworms, daphnia, baby brine shrimp, and grindal worms. Most wild-imported specimens refuse dry flakes outright, though a small number of long-term captive-bred lines will accept micro-pellets after patient weaning.

Best kept as a species-only pair or in a single male plus two or three females setup to reduce male-on-male aggression. A second male in a tank under 80 liters almost always ends in torn fins and a stressed dominant fish. The species tank approach also eliminates competition for food, which matters when your fish have mouths smaller than a grain of rice.

Tankmate Options and Weekly Routine

Suitable companions are limited to other tiny blackwater inhabitants like Boraras rasboras or Caridina shrimp, provided shrimp are not intended as food. Many keepers run dedicated species tanks because mixing risks the gouramis being outcompeted at feeding time or harassed by faster tankmates.

Weekly water changes of 10 to 20 percent using aged, tannin-rich water keep parameters stable, because these fish react poorly to any sudden shift in chemistry. Match the temperature and pH of the replacement water to the tank within 0.5 °C and 0.2 pH before adding it. Skip this step and you can lose a colony in a single afternoon.

• ▸Microworms and vinegar eels: ideal first foods for fry and a reliable staple for adults that ignore dry fare.
• ▸Baby brine shrimp: trigger strong feeding responses and provide the fats males need for display color.
• ▸Daphnia and grindal worms: round out the diet with fiber that keeps the digestive tract moving.
• ▸Aged leaf litter: serves as both décor and a slow-release source of tannins and microbial grazing.
• ▸Indian almond leaves: replace every 2 to 3 weeks to maintain steady humic acid release.

Breeding Behavior and Raising the Fry

Males construct small bubble nests tucked inside caves, coconut shells, or overturned flower pots and then coax females to spawn beneath them. The nest is often less than 2 cm across and hidden so well that you may not see it until fry are already hanging from the ceiling.

After spawning the male guards the eggs and tends the fry for up to two weeks, becoming intensely territorial and best separated from the female. Some breeders remove the female immediately after spawning; others leave her in caves with multiple exits to dodge the male’s advances. The right choice depends on the individual fish.

Eggs, Fry, and Pair Formation

Eggs hatch in roughly 24 to 48 hours, and fry require infusoria or liquid fry food for the first days before graduating to newly hatched brine shrimp. The free-swimming stage begins around day 4 to 6, and the male continues to gather strays back into the nest until they become fully mobile around day 10.

Success depends on stable parameters, abundant cover, and the patience to wait weeks or months for a compatible pair to form. Rushed introductions usually end in a female hiding until she is rescued or a male so stressed that he never colors up. Set up multiple small breeding tanks and let the fish choose their own partners when possible.

Once your colony is reproducing, the real question becomes what to do with all those fry and how to keep the species off extinction lists.

“Remove the male once the fry swim freely on their own.

Conservation Status, Sourcing, and What to Look For

Most Parosphromenus species are listed on the IUCN Red List as Endangered or Critically Endangered, and many are protected under CITES Appendix II. Habitat loss from logging, palm oil expansion, and peat drainage is the primary driver of population declines across the genus, with several species known only from a single remaining peat dome.

Prospective keepers should prioritize captive-bred stock from dedicated breeders, verify species identity, and confirm legal import documentation before purchase. Wild-caught fish often arrive stressed, carry internal parasites, and refuse prepared foods. A reputable breeder will provide locality data, spawn dates, and parent fish photos on request.

Red Flags and Conservation Impact

Avoid sellers who cannot name the species, the collection locality, or the generation of the fish. Prices well below market for the genus often signal wild-caught stock or misidentified juveniles. Organizations like the Parosphromenus Project maintain lists of breeders working with documented lines.

Keeping healthy populations in home aquariums doubles as a conservation measure, since each successful captive generation reduces pressure on wild populations. A single breeding pair that produces 20 fry every two months can rebuild a local population in a year, and surplus fish shared with other keepers compound the effect across the hobby.

That ripple effect is really what this hobby is about, and it reframes everything we’ve covered.

The Big Picture

Licorice gouramis reward keepers who treat water chemistry as the foundation rather than an afterthought, who feed live foods without exception, and who build the tank around leaf litter and dim light rather than bright gravel and plastic plants. The payoff is a small, display-worthy fish that colors up dramatically when conditions are right and breeds readily in mature setups. Pick captive-bred stock, verify the species, and commit to the blackwater routine before bringing any home.

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