Opaline Gourami Care Guide: Tank Size, Diet, and Compatibility Tips

Species Overview#

Opaline gouramis (Trichopodus trichopterus) are one of the most striking color morphs in the freshwater hobby. Their marbled blue and silver pattern swirls across the body in irregular bands and blotches that catch light differently from every angle, which is why retailers often charge a few dollars more for them than the wild-type fish. Underneath the showy coloration, they are the same hardy, semi-aggressive labyrinth fish that has been a community-tank staple in the US since the 1950s.

The species comes from slow-moving, vegetation-choked water across Southeast Asia. That history shapes everything about how you should keep them — warm water, dense planting, calm surface, and tank mates that will not pick a fight with a 5-inch fish that grows bolder with age.

Adult size

5–6 in (13–15 cm)

Lifespan

4–6 years

Min tank

30 gallons (single or pair)

Temperament

Semi-aggressive (males)

Difficulty

Beginner

Diet

Omnivore

Wild Origin & Natural Habitat#

Wild T. trichopterus populations live across Thailand, Malaysia, Vietnam, Cambodia, Laos, and parts of Indonesia. They occupy slow rivers, swamp forests, flooded rice paddies, and irrigation ditches — habitats that turn warm, stagnant, and oxygen-poor during the dry season. To survive in water that would suffocate most fish, the species evolved a labyrinth organ: a folded, lung-like structure behind the gills that lets it gulp atmospheric air directly from the surface. That single adaptation is why opaline gouramis can shrug off conditions that would kill tetras and rasboras outright.

The marbled opaline pattern does not exist in nature. It was selectively bred from the wild three-spot phenotype in the second half of the 20th century, and most opaline stock available in US stores today comes from commercial breeders in Southeast Asia and Florida.

Appearance & Color Morphs#

The opaline pattern is a swirling, iridescent blue-and-white marbling that covers the entire body. Unlike the wild type, opalines do not show two clean lateral spots — the marbling masks them entirely. Under good aquarium lighting, the blue takes on a near-violet sheen, especially in mature males. Other common morphs of the same species include:

• Three Spot (wild type): Pale silver-blue with two clean dark spots aligned along the body.
• Gold: Yellow-orange body with faint vertical bars and faded spots.
• Cosby: Heavier marbled pattern, often sold as "platinum opaline" in some shops.

All four morphs interbreed freely — fry from a mixed pairing can show any combination of patterns. Pricing typically runs $4–$10, with opalines and golds usually at the higher end of that range.

Size & Lifespan#

Adults reach 5–6 inches under good conditions, with males slightly larger and more elongated than females. In captivity, expect a 4–6 year lifespan. Fish kept in cramped 10-gallon setups rarely make it past three years; a properly sized 30-gallon-plus tank with stable parameters routinely produces fish that hit the upper end of the lifespan range.

Water Parameters & Tank Requirements#

Opaline gouramis are forgiving, but "forgiving" is not the same as "indestructible." Get the tank size and surface access right, and the rest is straightforward.

Ideal Water Conditions#

The species tolerates a wide parameter range, which is one of the main reasons it became a beginner staple. Stability matters more than hitting an exact number on the test kit.

Cycle the tank fully before adding livestock. Zero ammonia, zero nitrite, measurable nitrate — that is the only safe baseline for a new aquarium.

Minimum Tank Size & Layout#

A 30-gallon tank is the practical minimum for one opaline gourami or a male-female pair. A 55-gallon-plus tank is what you want for a small group or a community setup with several other species. Length matters more than height — these fish patrol horizontally and need swimming room.

Aquascape with tall background plants like Amazon sword, vallisneria, and hornwort. Add floating cover (Amazon frogbit, red root floaters, or a clump of hornwort left untethered) so females and subdominant fish have somewhere to escape male attention. Keep the mid-tank open for swimming; do not pack every square inch with hardscape.

Filtration & Surface Agitation#

A hang-on-back filter rated for your tank volume works well. Sponge filters are fine for breeding setups. Whatever you choose, baffle the output if it produces visible surface chop — opaline gouramis dislike strong flow and need a calm patch of surface where they can gulp air comfortably.

The labyrinth organ requires unobstructed access to the air above the water line. Leave at least a half-inch gap between the water surface and the tank lid. The air pocket above the surface should stay warm and humid. Cold drafts hitting the labyrinth organ — from an open window, an AC vent, or a lid pulled wide for feeding in winter — can cause respiratory damage that kills the fish over the following weeks.

Diet & Feeding#

Opaline gouramis are omnivores and will eat almost anything that fits in their mouth. The most common feeding mistake new keepers make is overfeeding, not underfeeding.

Omnivore Diet Staples#

Build the diet around a high-quality flake or micro pellet as the daily staple — look for whole fish or insect meal as the first ingredient on the label. Supplement two or three times per week with frozen bloodworms, brine shrimp, or daphnia for protein and enrichment. Add blanched zucchini, shelled peas, or a spirulina wafer once or twice weekly. Vegetable matter helps prevent constipation and bloat, both of which are common problems in overfed gouramis.

Live foods like mosquito larvae or live brine shrimp are excellent for conditioning breeding pairs but are not required for routine care.

Feeding Schedule & Quantity#

Feed adult opaline gouramis once or twice daily. Each feeding should be the amount your fish finish completely within two to three minutes. Anything left over after that fuels ammonia, not your fish. Skip one feeding per week — a weekly fasting day clears the digestive tract, reduces bloat risk, and matches the boom-bust feeding rhythm these fish would experience in the wild.

Tank Mates & Compatibility#

Opaline gouramis are sold as community fish, but the "semi-aggressive" label is real. Adult males in particular grow territorial and will harass smaller, slower fish. Plan stocking around their adult temperament, not their juvenile shop behavior.

Aggression Profile#

Males defend a territory that can occupy a third or more of a 30-gallon tank, especially when bubble-nesting. They will chase other male gouramis on sight, regardless of color morph, and they routinely nip the long, flowing fins of slower species. Females are more peaceful but will still squabble in the absence of cover. The aggression ramps up sharply as fish mature past the 3-inch mark, so a tank that looks calm in week one can turn hostile by month four.

Recommended Tank Mates#

Pair opaline gouramis with fish that occupy a different water column level and can hold their own around a 5-inch tank mate:

• Corydoras catfish — bottom-dwellers that stay out of the gourami's territory entirely.
• Larger tetras — black skirt tetras, lemon tetras, and rummy-nose tetras swim in mid-water and ignore the gourami.
• Larger barbs — cherry barbs and rosy barbs are calm enough to coexist; tiger barbs are not.
• Rainbowfish — boesemani and turquoise rainbowfish are fast, peaceful, and color-coordinate well.
• Kuhli loaches and yoyo loaches — bottom-dwellers that stay out of the way.
• Bristlenose plecos — armored algae eaters that do not provoke aggression.

Keeping Multiple Opaline Gouramis#

If you want a group, plan for 55 gallons minimum with heavy planting that breaks sight lines. Stock one male with two to three females — the extra females spread out the male's attention and prevent any one fish from being constantly chased. Two males can sometimes coexist in a 75-gallon-plus tank with enough cover, but expect occasional injuries and be prepared to remove the loser if a serious fight breaks out.

For a side-by-side look at species, water parameters, and stocking ratios across the family, see our gourami fish care guide. Beginners often start with the smaller, gentler dwarf gourami or honey gourami before moving up to the larger semi-aggressive T. trichopterus morphs.

Breeding#

Opaline gouramis are bubble-nesters, and home breeding is achievable in a dedicated 20-gallon setup. Fry from an opaline pairing can show any of the parent morphs — opaline, three-spot, or even gold — depending on the genetics in the line.

Bubble Nest Building#

Move a conditioned pair to a 20-gallon breeding tank with the water lowered to about 8 inches and the temperature raised to 78–82°F. Add floating plants — duckweed, frogbit, hornwort, or water lettuce — to give the male anchor points for the nest.

The male builds a bubble raft at the surface over one to two days by gulping air and coating each bubble with a mucus secretion. A male constructing frequent, well-formed nests is healthy, mature, and ready to spawn. Males in tanks with too much surface agitation often refuse to build at all.

Spawning & Fry Care#

When the female is ready, she swims under the nest, the male wraps around her in a nuptial embrace, and eggs are released and fertilized. The male catches sinking eggs in his mouth and spits them into the bubble nest. A single spawn can produce 500 to 800 eggs over several hours.

Remove the female immediately after spawning is complete. The male turns aggressive while guarding the nest and will kill her if she stays in the tank.

Eggs hatch within 24–36 hours at 80°F. Fry are free-swimming about three days post-hatch — remove the male at this point. Feed fry infusoria or commercial liquid fry food for the first 7–10 days, then transition to baby brine shrimp and crushed flake. Fry grow slowly; expect four to six months before they reach a sellable 1.5-inch size. A separate grow-out tank with a sponge filter keeps the fastest-growing fish from outcompeting their siblings.

Common Health Issues#

Ich & Velvet#

Ich (white spot disease): white salt-grain spots on fins and body, flashing against decor, clamped fins. Treat by raising the temperature gradually to 82–84°F over 24–48 hours and dosing aquarium salt or a malachite-green-based medication. Opaline gouramis tolerate heat treatment well, which is one advantage of working with a labyrinth fish over more sensitive species.

Velvet (Piscinoodinium): gold or rust-colored dust on the body, often visible only under a flashlight in the early stages. Velvet progresses faster than ich and is more dangerous. Treat with a copper-based medication, but remove any shrimp or snails first — copper is lethal to invertebrates.

Bacterial Infections & Fin Rot#

Fin rot and bacterial infections show up as red streaks on fins, ragged or eroding fin edges, ulcers on the body, or cottony patches. They almost always follow a stress event — a temperature swing, an aggressive tank mate, or a missed water change. Treatment starts with fixing the underlying cause: perform a 50% water change, correct any parameter problems, then dose a broad-spectrum antibiotic like kanamycin if symptoms persist after 48 hours. Catching fin rot early — when only the edges are frayed — is the difference between a quick recovery and losing the fin entirely.

Labyrinth Organ Sensitivity#

Cold drafts above the tank cause respiratory inflammation in labyrinth fish. Symptoms include heavy, labored breathing at the surface, gasping, and reluctance to gulp air. Prevention is straightforward: keep the tank lid closed during winter, position the aquarium away from windows and AC vents, and maintain a half-inch warm air gap between the water line and the lid. This is a real problem in open-top tanks placed in cold rooms — many a healthy gourami has been killed by a chilly draft from a cracked window in February.

Where to Buy & What to Look For#

Opaline gouramis are widely available across the US, but quality varies wildly between sources. The good news is that this is a tough enough species that even mass-bred fish from a chain store can live a full lifespan if you start with a healthy specimen and keep the water parameters stable.

Ask the staff if they quarantine new arrivals. A store that holds incoming fish for one to two weeks before selling them dramatically reduces your risk of bringing parasites or bacterial infections home to your display tank.

Price Range & Availability#

Expect to pay $5–$10 per fish at most US retailers. Opaline morphs typically command a $1–$3 premium over the wild-type three-spot fish, and store labeling can be inconsistent — what one shop sells as "blue gourami" may be tagged "opaline" three blocks away. Look at the pattern, not the tag. A solid blue-silver body with two visible dark spots is a wild-type three-spot or "blue" gourami. A swirled, marbled blue-and-white body with no defined spots is an opaline.

Acclimation#

Float the bag in your tank for 15–20 minutes to equalize temperature, then drip-acclimate over 30–45 minutes by slowly adding tank water. Net the fish out and discard the bag water — never pour store water into your display tank, since it can carry pathogens. See our how to acclimate fish guide for the full step-by-step.

For more on the broader family, see our gourami fish care guide, the sister color morph in the blue gourami care guide, or browse our full freshwater fish overview for other beginner-friendly community species.

Quick Reference#

• Tank size: 30 gallons minimum for one or a pair; 55+ for a group or community
• Temperature: 72–82°F (22–28°C)
• pH: 6.0–8.0
• Hardness: 5–30 dGH
• Diet: Omnivore — flake or pellet daily, frozen bloodworms/brine shrimp 2–3x weekly, vegetables 1–2x weekly
• Tankmates: Corydoras, larger tetras, cherry barbs, rainbowfish, kuhli loaches, bristlenose plecos
• Avoid: Other male gouramis, bettas, tiger barbs, angelfish, fancy guppies, aggressive cichlids
• Stocking: One male per tank, paired with two to three females in 55+ gallon setups
• Difficulty: Beginner
• Lifespan: 4–6 years