Poso halfbeak

Where they come from

Poso halfbeaks (Nomorhamphus celebensis) come from Sulawesi in Indonesia, around the Lake Poso area and nearby waterways. Think warm, clean water, lots of plant growth along the edges, and plenty of surface life to hunt. They are a neat oddball fish, and they act like it too - always watching the surface.

Setting up their tank

Give them more length and surface area than depth. They live in the top few inches most of the time, and they like room to cruise. I would not keep them in a tiny cube even if the gallons technically add up.

• Tank size: 20 long is a workable starting point for a small group, but 30-40 gallons makes them noticeably calmer and less nippy
• Cover: a tight lid is non-negotiable - halfbeaks jump, especially at feeding time or if they get spooked
• Flow: moderate is fine, but avoid blasting the surface so hard they struggle to hover
• Temp: mid-to-upper 70s F is where they act normal (around 24-27 C)
• Water: they do best in clean, stable water; neutral to slightly alkaline is usually easier than trying to force soft/acidic

Decor-wise, I like a planted layout with floating plants and some tall stems reaching the top. That breaks up sight lines and gives them a sense of cover without stealing their swimming lane. Leave open water at the surface - they want a clear runway.

What to feed them

These are surface micro-predators. Most of them ignore food that sinks, at least at first. If you only offer flakes that drop, you will swear they are not eating while your bottom fish get fat.

• Best staples: floating micro pellets, crushed floating pellets, and good quality flake that stays up top for a bit
• Favorite foods: live or frozen mosquito larvae, daphnia, baby brine shrimp, and small insects
• Treats: wingless fruit flies or tiny crickets (sparingly, and watch for overfeeding)

Feed small amounts more than once a day if you can. They are built for picking at the surface, not bulldozing one huge meal. If you are trying to get new fish eating, start with frozen foods at the surface and mix in pellets little by little.

How they behave and who they get along with

Poso halfbeaks are busy, curious, and a little pushy. Males in particular posture and squabble, and you will see lots of quick dashes and face-offs at the surface. In a cramped tank, that can turn into fin-nipping.

• Keep them in a group so one fish does not take all the heat
• Aim for more females than males if you can (males are the spicy ones)
• Pick tankmates that live mid-to-bottom and are not slow, long-finned, or easily stressed
• Avoid other surface fish (they will compete and bicker)

Good companions in my experience are small, calm bottom dwellers and midwater fish that do not hang at the surface. Think small loaches, Corydoras in the right temperature range, or sturdy small rainbowfish that stay mostly midwater. Skip bettas, fancy guppies, and anything with flowing fins - halfbeaks will test them.

Breeding tips

They are livebearers, and if they are comfortable you may get surprise babies. The fry are fairly large compared to many livebearers, but they are still on the menu if the adults feel like it.

• Condition adults with small live/frozen foods (daphnia and baby brine shrimp work great)
• Provide floating plants and dense surface cover for fry to hide in
• If you want to raise numbers, move a gravid female to a separate tank with gentle filtration and lots of floaters, then return her after the drop
• Start fry on baby brine shrimp, microworms, or finely crushed floating foods

Do not expect a huge drop like with guppies. I have usually seen smaller broods, and the timing can feel unpredictable. Stable water and consistent feeding seem to matter more than chasing some magic parameter.

Common problems to watch for

• Jumping: the number one halfbeak killer in home tanks
• Starving in a community tank: they miss sinking food and get outcompeted at the surface by faster fish
• Fin nipping and stress: usually from too-small tanks, too many males, or too-bright/open setups with no surface cover
• Skinny disease look: often just not eating enough, but also watch for internal parasites if appetite drops and weight keeps falling
• Mouth injuries: they can scrape their beaks on hard decor or the lid during panicked dashes

The big success pattern with this species is simple: calm surface, lots of cover up top, food that stays afloat, and enough room so they are not constantly in each other’s faces. Do that, and they are a really fun fish to watch day to day.