Golden pencilfish

1) Where they come from

Golden pencilfish (Nannostomus beckfordi) come from northern South America—think slow, tannin-stained creeks and flooded forest edges in places like Guyana and the Amazon basin. The water’s often tea-colored from leaf litter, with lots of roots, sticks, and plants breaking up the flow.

2) Setting up their tank

These are small fish, but they look way better (and behave better) in a group. I’d treat them like a display shoal fish: give them horizontal swimming room and lots of visual breaks so the shy ones don’t feel exposed.

• Tank size: 10–20 gallons works great for a group; bigger is always nicer for calmer behavior
• Group size: 8+ if you can—6 is okay, but you’ll see more confidence in larger groups
• Filtration: gentle flow; they don’t love being blasted around
• Hardscape: driftwood, branches, leaf litter (Indian almond leaves or oak), and floating plants
• Lighting: medium to low; floaters help a lot

For water, they’re pretty forgiving for a beginner fish as long as you don’t swing parameters all over the place. Neutral-ish water is fine. If your tap is hard, they can still do okay—just keep things stable and don’t chase numbers.

3) What to feed them

They’ve got small mouths and they’re picky about particle size. Mine would take flakes, but only once I crushed them up. If you want that warm golden color and steady activity, mix in small frozen/live foods.

• Everyday: finely crushed flake or micro pellets
• Favorites: baby brine shrimp, daphnia, cyclops, and small frozen foods
• Treats: live baby brine shrimp or microworms (they go nuts for it)

4) Behavior and tankmates

Golden pencilfish spend a lot of time in the upper half of the tank, kind of hovering and making short darts. Males do little sparring displays—more like “posturing” than real fighting. In a good-sized group with cover, it’s fun to watch and usually harmless.

• Great tankmates: small tetras, Corydoras, otos, small rasboras, peaceful dwarf cichlids, and shrimp-friendly setups (with enough plant cover)
• Avoid: fin nippers, big boisterous fish, and anything that sees tiny fish as snacks
• With shrimp: adults often fine; shrimplets may get picked off unless you’ve got dense moss and hiding spots

5) Breeding tips

They’re one of the more doable pencilfish to breed, but don’t expect a big spawn in the community tank—eggs and fry tend to get eaten. If you actually want babies, a small breeding setup makes life way easier.

• Use a separate tank: 5–10 gallons with a sponge filter and gentle air
• Spawning medium: fine-leaf plants, a thick clump of moss, or a spawning mop
• Lighting: dim (or keep it darker with floaters)
• Condition the parents: baby brine shrimp/daphnia for a week or two
• Pull the adults after you see spawning behavior— they won’t babysit

Fry are tiny at first. You’ll need truly small foods: infusoria, commercial fry dust, or a mature tank with biofilm helps. Once they can take baby brine shrimp, things get much simpler.

6) Common problems to watch for

Most issues I’ve seen with golden pencilfish come from stress: too bright, too exposed, not enough of a group, or being housed with pushy tankmates. They’re hardy once settled, but they don’t love chaos.

• Jumping: happens during chasing or sudden scares—use a lid and keep the waterline a little lower
• Faded color/hiding: usually too much light or not enough cover (or too small a group)
• Not eating: food pieces too big, or they’re being bullied/offered food in strong flow
• Ich after adding new fish: they can show spots fast when stressed—quarantine new arrivals if you can
• Slow wasting/skinny fish: sometimes internal parasites on new imports; look for stringy white poop and poor appetite