Bunguran rasbora

Where they come from

Bunguran rasbora (Rasbora bunguranensis) is one of those Borneo gems that still feels a bit "under the radar." They come from Bunguran Island (Natuna Islands, Indonesia), in the kind of small forest streams and swampy side waters where the light is dim, the bottom is leaf litter, and the water is usually soft and on the acidic side.

That background matters because they act like fish that are used to cover and calm water. Give them that vibe and they settle in way faster.

Setting up their tank

Think "small, shaded stream" more than "bright planted display." They will live in a regular community tank, but they look and behave better if you lean into their natural setup.

• Tank size: I would start with 20 gallons for a proper group, bigger is always easier to keep stable.
• Group size: 10+ if you can. They get braver, color up more, and you see more natural schooling.
• Filtration: gentle to moderate flow. A sponge filter or a small canister with a spray bar works well.
• Lighting: moderate to low. Floating plants help a lot if your light is bright.
• Decor: fine sand or small gravel, driftwood, leaf litter (catappa/Indian almond, oak, beech), and dense plants around the edges with open swimming space in the middle.

Water-wise, they really appreciate softer water. Neutral can work, but if your tap is hard and alkaline, expect them to be more skittish and a bit harder to condition. I kept mine most comfortably in the mid-70s F, with soft water and a slightly acidic pH. Stability matters more than chasing exact numbers, but they are not the fish I would pick for liquid-rock water.

What to feed them

They are classic small rasboras: tiny mouths, constant nibblers, and way happier on a rotation than on one dry food forever. If you want them to color up and fill out, feed smaller foods more often rather than one big meal.

• Daily staples: quality micro pellets, finely crushed flakes, small granules.
• Frozen: baby brine shrimp, cyclops, daphnia, finely chopped bloodworms (not as the main food).
• Live (if you can): baby brine shrimp, grindal worms, microworms, daphnia.

One thing I learned the hard way: they will absolutely overeat if you let them. Keep portions tight. A little belly is fine, but if they start looking thick behind the head, back off and add more daphnia-style foods.

How they behave and who they get along with

These are peaceful, midwater schooling fish. In a good-sized group they are active and confident, and they do that loose "wave" formation rasboras are known for. In small numbers they get shy and spend too much time hiding.

Tankmates should be calm and not pushy at feeding time. They do best with other gentle fish from similar water: small rasboras, peaceful danios (the calmer ones), pygmy corydoras, otocinclus, and small gouramis that are not bullies. Shrimp can work if the tank is planted and you have lots of cover, but babies may disappear.

• Avoid: big active barbs, fin nippers, chunky livebearers in hard water setups, and anything that treats small fish like snacks.
• Best look: species group or a Borneo-style community with other soft-water fish.

Breeding tips

Breeding them is doable, but it is not usually an "oops babies" fish like some egg scatterers. If you want fry, plan for it. Conditioning is half the battle: lots of small live/frozen foods and very clean water for a couple weeks.

• Setup: a separate breeding tank is your friend. Dim light, soft water, and a gentle sponge filter.
• Spawning site: fine-leaved plants (java moss works), or a spawning mop. Some folks use a mesh or marbles to protect eggs from the adults.
• Pair/group: you can try a conditioned pair, or a small group with more males than females and pull adults after spawning.
• Egg/fry care: remove adults after you see spawning behavior. Keep the tank darkish at first and avoid strong flow. Start fry on infusoria/microfoods, then baby brine shrimp once they can take it.

Common problems to watch for

Most issues I have seen with these come from stress, shipping, and running them in water that does not match what they are used to. They are not fragile, but they do not shrug off rough starts like some hardier schoolers.

• Skinny new fish that will not eat: often shipping stress or internal parasites. Try calm surroundings, smaller foods, and consider a quarantine and deworming plan if they do not improve.
• Ich/white spot after adding them: very common with stressed imports. Quarantine helps, and keep temperature stable.
• Wasting away over weeks: suspect internal parasites. Watch for stringy white poop and weight loss despite eating.
• Clamped fins and hiding: usually too bright, too few fish, or a pushy tankmate.
• Jumping: they can bolt when spooked. Use a lid, especially the first couple weeks.

If you give them a mature, slightly shaded tank, keep them in a real group, and feed small foods they can actually grab, Bunguran rasboras are one of those fish that quietly become favorites.