Neon Green Rasbora

1) Where they come from

Neon Green Rasboras (Microdevario kubotai) come from Thailand and nearby areas, hanging out in small, slow-moving waters with lots of plants and leaf litter. That bright green color looks “too electric to be real,” but in the right tank it’s the real deal.

2) Setting up their tank

These are small fish, but they don’t look their best in tiny setups. Give them some horizontal swimming room and they’ll school nicely instead of scattering into corners.

• Tank size: 10 gallons works, 15–20 gallons looks way better for a group
• Group size: 8 minimum, 12–20 is where you start getting that “shimmering green cloud” effect
• Filter: gentle flow (sponge filter or a baffled HOB). They don’t love being blasted around
• Plants: the more the better—fine-leaf plants, moss, floating plants, and some open space up front
• Substrate/decor: dark substrate and some wood/leafy cover will make their color pop

For water, they’re forgiving as long as you’re consistent. Mine have done well in slightly soft to neutral water. Aim for something like 22–26°C (72–79°F), and keep nitrates low with regular water changes.

3) What to feed them

They’ve got tiny mouths, so think “micro foods.” If you only offer big flakes, they’ll still eat, but you’ll see more leftovers and less belly-filling.

• Staples: crushed flake, micro pellets, powdered fry food (great for small mouths)
• Frozen: baby brine shrimp, cyclops, daphnia (awesome for color and conditioning)
• Live (if you can): baby brine shrimp or microworms—they go nuts for it

4) Behavior and tankmates

Kubotai are peaceful, fast, and a little shy at first. In a proper group they spend most of their time mid-water, flashing green as they turn. If you keep too few, they get jumpy and hide more.

• Great tankmates: other small, calm fish (ember tetras, celestial pearl danios, small rasboras), otocinclus, shrimp (adult shrimp usually fine)
• Also good: small corydoras like pygmy or habrosus
• Skip: big or nippy fish (most barbs, large danios, aggressive gouramis), and anything that thinks a 2 cm fish is lunch

5) Breeding tips (if you want to try)

They’re egg scatterers. Spawning isn’t the hard part—raising the babies is. In a community tank, the eggs and fry usually get eaten before you ever notice.

• Condition adults with frozen/live foods for a week or two
• Set up a small breeding tank with moss or a spawning mop (and ideally a mesh/egg grate so eggs fall out of reach)
• Use gentle filtration (sponge filter) and keep the tank clean
• After you see spawning behavior, pull the adults—otherwise they’ll snack on the eggs
• First foods for fry: infusoria/liquid fry food, then baby brine shrimp once they’re big enough

6) Common problems to watch for

Most issues with kubotai come from stress: too few fish, too much open space, too much flow, or water that swings around. They’re small, so they show problems faster than bigger fish.

• Faded color / hiding: usually small group size, bright bare tank, or bullying tankmates
• Deaths soon after purchase: new arrivals can be sensitive—go slow on acclimation and keep the tank stable
• Ich after adding new fish: quarantine new additions if you can; these little guys don’t love meds at “nuke the tank” doses
• Wasting away / skinny bellies: internal parasites happen—watch for fish that eat but don’t gain weight
• Fin nips: usually from inappropriate tankmates, not from kubotai themselves