Intermedia lebiasina

Where they come from

Lebiasina intermedia is one of those South American "pencil"-type characins from flowing rainforest waters. Think clear to lightly tea-stained streams, lots of overhanging plants, leaf litter, and that constant gentle push of current. They act like fish that grew up dodging shadows and feeding off stuff that drops in from above - because they did.

Setting up their tank

Give them length and cover. I would not do these in a small cube. A 30-40 gallon breeder works, but a 4 foot tank is where they start acting normal - cruising, sparring a bit, and not freaking out every time you walk past.

• Tank size: bigger footprint beats tall. Aim for 36-48 inches of swimming room if you can.
• Flow and oxygen: moderate current with a decent filter and/or powerhead. They look sharper and breathe easier in well-aerated water.
• Hardscape: sand or fine gravel, driftwood branches, leaf litter if you like that look, and plants to break up sight lines.
• Cover: floating plants or tall stems help a ton. They are surface-oriented and relax more with shade.
• Lid: tight-fitting. They can and will jump if spooked.

Water wise, they do best on the soft/acidic side, but stability matters more than chasing a magic number. I have had the best luck keeping them in clean, low-nitrate water with regular water changes. If your tap is hard, you may need to cut it with RO so they are not living in liquid rock.

What to feed them

They are micropredators. Mine ignored a lot of typical community flakes at first, then slowly learned, but they always colored up and behaved better on real food.

• Staples: high-quality small pellets and crisp flakes (once they recognize it as food).
• Best frozen: bloodworms, daphnia, brine shrimp, cyclops, chopped mysis (for larger adults).
• Best live: baby brine shrimp, grindal worms, small insects if you culture them.

Feed small amounts a couple times a day if you can. They are mid-to-upper water pickers, so foods that hang in the water column get taken faster than stuff that rockets to the bottom.

How they behave and who they get along with

Expect a mix of "schooling fish" and "small predator" behavior. They cruise together, but males also posture, chase, and spar. In a roomy tank with cover, that is normal and pretty fun to watch. In a tight tank, it turns into constant stress.

• Keep them in a group: 6+ is a good start. Larger groups spread out the attention and calm the vibe.
• Best tankmates: other calm, similar-size fish that like soft water - peaceful tetras, hatchetfish, Corydoras, small Loricariids.
• Avoid: slow long-finned fish (they can get harassed), tiny shrimp or microfish (may become snacks), and pushy fin-nippers (they will not enjoy being out-nipped).

They spend a lot of time near the surface and midwater. If you pack the tank with surface-feeders that outcompete them, they will get thin. Make sure food actually reaches them.

Breeding tips

Breeding Lebiasina can be done, but it is not a casual "oops babies" fish. The adults are opportunistic and the eggs are not safe in a typical display tank. If you want a real shot, plan a separate setup.

• Breeding tank: dim, mature sponge filter, lots of fine-leaf plants or spawning mops, and a tight lid.
• Conditioning: heavy feeding on live/frozen for 1-2 weeks, with frequent small water changes.
• Trigger: slightly cooler water change followed by a gradual warm-up often gets activity going.
• Egg safety: remove adults or use a mesh/egg crate barrier so they cannot pick the eggs off.

Fry are tiny and need tiny food. If you cannot produce infusoria/microworms or have a plan for first foods, you will lose most of them early.

Common problems to watch for

• Jumping and injuries: the #1 killer in my experience. Lids, calm lighting, and minimizing spooks prevent most of it.
• Thin fish that never fill out: usually from competition at feeding time, stress from too-small groups, or parasites if they keep eating but do not gain.
• Fin damage from sparring: normal nicks happen, but shredded fins usually means the tank is too small or too bare.
• Ich and other outbreaks after purchase: they are sensitive to stress swings. Quarantine helps a lot, and keep the first weeks calm and stable.
• Nitrate creep: they get "off" faster than many tetras when water quality slides. Regular water changes and not overfeeding go a long way.

If something looks wrong, look at the basics first: are they being outcompeted for food, do they have enough cover, and are you letting nitrates climb? Fixing those three usually does more than throwing meds at the tank.