Allen's river garfish

Where they come from

Allen's river garfish (Zenarchopterus alleni) comes from northern Australia, cruising slow rivers, billabongs, and weedy backwaters. If you picture warm water with lots of cover at the edges and a gentle flow, you're basically there. They spend a ton of time right under the surface, picking off small prey and insects.

Setting up their tank

Give them length over height. They use the top 2-3 inches of the tank like its their highway, and they spook easily. For a small group, I'd start at 4 ft long (around 55-75 gallons) and bigger is genuinely easier because they can spread out and you get fewer panic sprints.

• Tank: long footprint, lots of open surface lane
• Lid: tight-fitting, no gaps around filters or airline holes (they jump like arrows)
• Flow: gentle to moderate, nothing that pins them at the surface
• Lighting: not super bright unless you break it up with floaters
• Filtration: oversized but with intake protection (pre-filter sponge)

Decor-wise, think edge cover. I like a mix of fine-leaved plants (or artificial ones if you can't keep plants) plus some floating plants to calm them down. Keep the middle and surface mostly open so they can cruise without smacking into hardscape.

Water-wise, warm and stable beats chasing exact numbers. I kept mine in the mid-to-high 70s F and they were much calmer once the tank was mature. Freshwater is fine, but they don't love big swings. If your tap is on the hard side, they usually handle it better than rapid pH bouncing from tinkering.

What to feed them

They're visual, surface-feeding predators. Mine ignored food that sank, and they were picky about anything that didn't move. Plan around that and feeding gets a lot easier.

• Great staples: live/frozen mosquito larvae, daphnia, brine shrimp, chopped bloodworms (offered at the surface)
• Meaty options: small crickets or flightless fruit flies (for larger individuals), chopped prawn/shrimp as an occasional treat
• Training foods: floating micro-pellets or small floating sticks - sometimes they learn, sometimes they never do

A trick that worked for me: use a feeding ring or a clear tube to keep food at the surface so it doesn't get dragged into the filter. If you're offering frozen, thaw it and gently pour it right into the ring. They learn the spot fast.

How they behave and who they get along with

They look sleek and calm, but they're skittish. Sudden movements, loud lid clanks, or a net in the water can set off the full-speed surface dash. In a settled tank with cover, they spend the day cruising and doing that cool angled hover just under the film.

They do best in a group, but you want space. In cramped tanks, you may see chasing and fin-nipping. With room and line-of-sight breaks (plants, floaters), they usually sort themselves out.

• Good tankmates: calm mid-water fish that won't harass them (larger rainbows, peaceful barbs, sturdy tetras in big tanks), bottom fish that mind their business (loaches, Corydoras that like warmer water)
• Avoid: fin-nippers, hyper surface feeders, aggressive cichlids, anything small enough to fit in their mouth
• Also avoid: jumpy fish that startle the whole tank every 10 minutes

Breeding tips

Breeding Zenarchopterus in home aquariums is possible, but its not a casual weekend project. The big challenge is getting a settled group, lots of live food, and the right social mix. If you buy juveniles and raise a group, your odds are way better than trying to pair off adults.

If you want to try, set up a species-focused tank: floating plants, gentle filtration, and very clean water with frequent small water changes. I had the best behavior (more displaying, less spooking) with dimmer light and heavy surface cover.

• Start with a group so you likely get both sexes
• Condition with tons of live/frozen foods at the surface for several weeks
• Give them quiet time - they breed more readily in tanks with low traffic and stable routines
• If you see fry, separate adults or move fry to a grow-out tank and feed tiny live foods (baby brine, microworms)

Common problems to watch for

Most issues I saw were husbandry and handling problems, not mystery diseases.

• Jumping and impact injuries: the #1 killer - caused by gaps in lids, sudden lights-on, chasing, or spooking
• Starvation in 'community' tanks: they lose out at feeding time if food sinks or faster fish steal everything
• Mouth and snout damage: from slamming into glass during panic sprints or from rough netting
• Surface film and low oxygen: they hang at the surface anyway, so a stagnant top layer can stress them fast
• Internal parasites (wild fish): weight loss despite eating, stringy poop - quarantine helps a lot

If one is acting shy and staying pinned in a corner, check the obvious stuff first: surface agitation, ammonia/nitrite (even tiny spikes), and whether its actually getting food. Once they're confident and well-fed, they're surprisingly hardy - but they won't forgive sloppy surface access or a sketchy lid.