Emerald Betta (Betta smaragdina)
Betta smaragdina
Min Tank Size
75L
Adult Size
6.5 cm
Lifespan
4 years
About
Native to rice paddies, slow streams, and roadside ditches across northeastern Thailand and into Laos, Betta smaragdina is one of those fish that stops you in your tracks. Males flash scales that shift from deep teal to brilliant emerald green depending on the light, with red-edged fins and that characteristic betta attitude. Females are far more subdued but still carry hints of iridescence. They grow to around 6.5 cm and are noticeably more robust than the domestic betta you'd find in a pet store cup.
Water conditions don't need to be extreme. A pH between 6.0 and 7.5 works fine, and they're tolerant of a reasonable GH range, though softer water closer to their natural habitat seems to bring out their best color and breeding behavior. Temperature between 22 and 28 degrees Celsius suits them well. Filtration should be present but gentle. These fish come from sluggish water and strong flow stresses them out.
Diet-wise, they're true carnivores. Live and frozen foods like bloodworms, daphnia, and mosquito larvae are eagerly accepted and should form the backbone of their diet. Pellets can work for some individuals, especially tank-raised ones, but don't expect every fish to adapt quickly.
What makes smaragdina genuinely interesting to keep is that unlike domestic bettas, males can sometimes coexist in a well-planned planted tank with enough space and visual breaks. It's not guaranteed, but it's possible, which opens up some really striking display tank possibilities. Browse community builds featuring this species and you'll see some beautifully aquascaped setups that highlight just how good a thriving group can look.
Water Parameters
Temperature
°CpH
GH
dGHKH
dKHSwimming Level
Flow Preference
Keeping multiple Emerald Betta (Betta smaragdina) together
Emerald Betta (Betta smaragdina) is strongly territorial. Multiples fight over space unless the tank is large enough for each to claim its own area. A single individual is the safer default.
Compatibility
Smaragdina work well with small, fast-moving fish that occupy the mid and lower zones, think small rasboras, ember tetras, pygmy corydoras, or otocinclus. These companions don't compete for space at the water surface and are too quick to be harassed. Avoid slow, long-finned tankmates like guppies or other bettas, as fin nipping from the smaragdina is unlikely but the visual similarity to rival males can trigger aggression. Dwarf shrimp are not safe regardless of tank size. Larger ornamental shrimp like Amano shrimp have a better survival rate but still carry some risk. Snails are fine.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The most common mistake is keeping them in conditions suited for domestic bettas, specifically tiny tanks with still water and no complexity. Smaragdina need room to establish loose territories and respond badly to cramped, featureless setups. A second common issue is diet. Relying solely on betta pellets often produces dull coloration and low activity. Incorporating frozen or live foods makes a visible difference. Wild-caught specimens can be stubborn about accepting prepared food, so have daphnia or mosquito larvae on hand when acclimating new arrivals. A lid is non-negotiable. These fish jump.
Behavior & Aggression
Male smaragdina will square off with each other, flaring and sparring, but compared to domestic bettas the encounters rarely escalate to serious injury. The key variable is space. In a tank under 75 liters with nowhere to escape, a dominant male will persistently harass subordinates. Give them thick plant cover, floating plants, and broken lines of sight and the dynamic changes considerably. Two males in a small bare tank is a bad idea. Five males in a heavily planted 150-liter setup often works. They're not typically aggressive toward other species, though anything small enough to eat is at risk.
Things to Know
- Males will fight if they cannot establish visual separation in the tank.
- Will hunt and eat small shrimp, including dwarf species.
- Capable jumper, always use a tight-fitting lid.
- Wild-caught individuals may refuse dry food initially.
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