Glass blue-eye
Kiunga ballochi
The Glass blue-eye exhibits a slender body with striking iridescent blue and green scales, highlighted by a distinctive dark spot on its operculum.
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About the Glass blue-eye
This is a tiny little PNG blue-eye with a mostly see-through body and subtle yellow-and-black fin markings that look really slick when a group is sparring and flashing. In the wild its range is extremely small (Upper Fly River system near Kiunga/Tabubil), so its basically a conservation fish as much as an aquarium fish. If you ever run into them, think calm, planted, clean-water setup and a decent-sized group so they feel secure.
Also known as
Quick Facts
Size
3 cm SL (about 1.2 inches)
Temperament
Peaceful
Difficulty
Advanced
Min Tank Size
15 gallons
Lifespan
2-4 years
Origin
Oceania (Papua New Guinea)
Diet
Micro-predator/omnivore - tiny live/frozen foods (baby brine shrimp, daphnia, cyclops) plus fine pellets/flakes
Water Parameters
24-26°C
7-8
5-28 dGH
Need a heater for this species?
This species needs 24-26°C in a 15 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give them a long tank with open swimming room and a lid - they are jumpy, especially when spooked by lights flipping on.
- Keep the water hard and alkaline (think pH around 7.5-8.5, moderate to high GH) and keep nitrates low; they get cranky fast in old, dirty water.
- They look best and act calmer in a group of 8-12+, and you will see more color once the pecking order settles.
- Feed small foods they can actually chase: baby brine shrimp, daphnia, cyclops, and fine micro pellets; hit them 2-3 times a day in small pinches instead of one big dump.
- Skip slow, long-finned tankmates and anything nippy - go with other quick, peaceful fish that like similar hard water, or keep them species-only if you want fewer headaches.
- They love flow and oxygen, so add a powerhead or strong filter return, but give them a calm corner with plants or spawning mops so they can take breaks.
- Breeding is doable if you condition them on live foods: they scatter adhesive eggs in fine-leaf plants/mops, and the adults will snack on eggs, so pull the mop daily or move the breeders to a separate tank.
Compatibility
Good Tankmates
- Other small rainbowfish, especially Gertrude's and threadfin rainbows - same vibe, they school up loose and stay in the top half. Keep them in a group so the blue-eyes are confident.
- Small, chill tetras like ember tetras or green neon tetras - active but not pushy, and they do not usually mess with the blue-eyes' fins.
- Micro rasboras (chili rasboras, phoenix rasboras) - peaceful little midwater fish that match their size and dont try to dominate feeding time.
- Corydoras (pygmy, habrosus, panda, etc.) - mellow bottom crew, totally ignore the blue-eyes, and keep the tank feeling busy without stress.
- Otocinclus - great algae crew for a planted setup, gentle as can be, and they wont compete much for the same food if you feed properly.
- Amano shrimp or nerite snails - the glass blue-eyes wont bother them in my experience, and they fit the peaceful planted community thing well.
Avoid
- Fin nippers like tiger barbs or serpae tetras - the blue-eyes are small and get ragged fast, plus they get shy and stop showing color.
- Bettas and other slow, fancy-finned fish - not because the blue-eyes are mean, but the mix gets weird: bettas can decide they own the top and start chasing.
- Big or boisterous fish like gouramis (larger kinds), cichlids, or anything that acts like the tank is theirs - the blue-eyes get pinned to the corners and miss meals.
Where they come from
Glass blue-eyes (Kiunga ballochi) are one of those New Guinea rainbowfish relatives that make you stop and stare. They come from the far south of Papua New Guinea around the Kiunga area, in small clear waters that can swing with seasons. They are not a "stick them in any community tank" fish - they do best when you lean into that clean, calm, well-established stream vibe.
If you have kept easier Pseudomugil and think this is the same deal, this one is pickier. The payoff is real, but you want a mature tank and steady routines.
Setting up their tank
Give them room to cruise and a lot of fine cover to duck into. I have had the best luck treating them like a small, fast schooling fish that hates surprises: stable water, gentle flow, and lots of plant or moss structure.
- Tank size: 20 gallons long is a nice starting point for a group, bigger if you want them really relaxed
- Group size: at least 10-12, and more is better (they act braver and color up more evenly)
- Filtration: a cycled sponge filter or a gentle canister with a spray bar - you want clean water without blasting them
- Flow: mild to moderate, aimed across the surface for oxygen and to keep food moving
- Lighting: moderate; they look best with darker substrate and plants to break up sightlines
- Plants and cover: Java moss, Subwassertang, fine-leaf stems, floating plants, and some twiggy hardscape
- Substrate: dark sand or fine gravel (mostly for your enjoyment - they do not dig)
- Water: keep it consistent; slightly acidic to neutral is where mine behaved best
Start them in a tank that has been running a while. New setups tend to swing (biofilm, microfauna, nitrates bouncing around), and this species seems to show stress faster than most little blue-eyes.
They are jumpers. Not always, but the day you leave a gap around the lid is the day one finds it. Cover the tank tightly and watch gaps around hoses and cords.
Do not gamble with "tiny" ammonia or nitrite. If your test kit shows either, pause feeding and fix the water quality first.
What to feed them
They are small-mouthed micropredators. If you feed like you would for nano tetras (mostly dry crumbs), they might survive, but they will look washed out and you will see more bickering. Live and frozen foods make a big difference.
- Best staples: baby brine shrimp (live), daphnia, cyclops, and small mysis (chopped if needed)
- Good frozen options: cyclops, baby brine shrimp, finely chopped brine, small plankton
- Dry food: high-quality micro pellets and fine flakes, but rotate with frozen/live
- Feeding rhythm: small amounts 2-3 times a day beats one big dump (they are constant pickers)
If you want them to settle in after shipping, baby brine shrimp is the fastest "switch" I know. They usually cannot resist it, and it gets shy fish out in the open.
How they behave and who they get along with
In a good-sized group they are busy, curious, and a little sparry with each other. Males display constantly, but it is more posturing than actual damage if the tank has cover and you are not understocked.
They do best with calm, similarly sized fish that will not outcompete them at feeding time. Fast pigs at the surface can starve them out without you realizing it.
- Good tankmates: small peaceful rainbows/blue-eyes, tiny rasboras, pencilfish, small Corydoras, Otocinclus (in stable tanks)
- Use caution: most livebearers (can be pushy at food), larger tetras, boisterous barbs
- Avoid: fin nippers, anything that sees them as snacks, and hyperactive fish that keep them pinned in corners
If they spend most of the day hiding, it is usually one of three things: too small a group, too bright and bare a tank, or tankmates that are making them nervous.
Breeding tips
They are egg scatterers and will spawn in fine plants and moss. The trick is not getting them to spawn - it is getting any eggs to survive in a community tank. Adults will pick at eggs and tiny fry if they find them.
- Spawning setup: a small tank with a seasoned sponge filter and a big wad of Java moss or spawning mops
- Breeders: a trio (1 male, 2 females) or a small group; feed heavy on live/frozen
- Egg collection: pull the mop/moss every day or two and move it to a hatch container with gentle aeration
- Hatching: keep water clean and stable; eggs usually take around 1-2 weeks depending on temperature
- First foods: infusoria and rotifers help, but baby brine shrimp is the workhorse once they can take it
If you see fungus on eggs, you are usually dealing with dirty water, dead eggs not being removed, or not enough gentle flow. A small air stone near (not blasting) the eggs helps a lot.
Common problems to watch for
Most issues with Kiunga ballochi trace back to instability: swings in temperature, missed water changes, overfeeding in a small tank, or a tank that is not fully cycled. They do not hide problems well.
- Wasting away despite eating: usually internal parasites or getting outcompeted at food; separate and treat if needed
- Clamped fins and skittish behavior: stress from bright/bare tanks, aggressive tankmates, or water quality swings
- Shimmying or flashing: often irritation from ammonia/nitrite, high organics, or sudden parameter changes
- Unexplained losses after water changes: temperature mismatch or big chemistry shifts; smaller, more frequent changes tend to work better
- Jumping: almost always a lid gap, or a sudden scare (lights snapping on, chasing, banging the glass)
Go easy on big rescapes and deep gravel vac sessions. If you stir up a lot of gunk at once, these fish can be the first to show it.
If you keep their world steady, feed small live/frozen foods regularly, and keep them in a real group, they repay you with constant displaying and that clean glassy-blue look that photos never quite capture.
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