Buffon's river-garfish

Where they come from

Buffon's river-garfish (Zenarchopterus buffonis) comes from coastal rivers, mangrove creeks, and brackish backwaters in Southeast Asia. Think slow-to-moderate current, lots of surface cover, and water that swings between fresh and salty with the tides.

They are surface fish to the core. If you set up the top foot of the tank well, you are halfway there.

Setting up their tank

Give them length more than height. These fish cruise and sprint along the surface, and in a short tank they bonk noses and stress out. A covered tank is non-negotiable - they jump, and they can clear gaps you would not expect.

• Tank size: I would start at 40 breeder/55 gallon for a small group, bigger if you can (their whole vibe is "room to run").
• Lid: tight-fitting with no gaps around hoses or cables.
• Filtration: strong biological filtration and steady flow, but aim the return so the surface is moving without blasting them like a river jet.
• Lighting: moderate; too bright with no shade keeps them edgy at the surface.
• Surface cover: floating plants (if they tolerate your salinity) or overhanging fake plants work great. They relax fast when they have a "ceiling".

For salinity, aim for a true brackish setup rather than "a little salt." I have had the best results around specific gravity 1.005-1.012, depending on tankmates. Mix marine salt (not table salt) and use a refractometer or hydrometer so you know what you are doing, not guessing.

• Temperature: 75-82F (24-28C)
• pH: usually 7.2-8.2 in brackish setups
• Hardness: moderate to hard is fine
• Specific gravity: 1.005-1.012 as a practical range for most hobby tanks
• Water changes: frequent smaller changes beat big swings (they hate sudden shifts in salinity and temperature).

What to feed them

They are surface micropredators. Mine ignored most sinking foods and acted like pellets did not exist until they learned. Live and frozen foods get them started fast, and once they are confident you can usually transition them to better staples.

• Best starters: live or frozen baby brine shrimp, mysis, chopped krill, daphnia, blackworms (rinse well)
• Great staples once they accept them: floating carnivore pellets, small floating sticks, gel foods formed into tiny bits
• Treats: small insects (flightless fruit flies), chopped prawn, fish eggs (sparingly)

Watch them eat. You want to see quick snaps at the surface and bellies that look gently rounded, not sunken behind the head. If the bolder fish hog everything, spread food along the whole length of the tank so the shy ones get a shot.

How they behave and who they get along with

They are alert, fast, and a little twitchy until they settle in. In a calm, well-covered tank they become confident cruisers and you will see a lot of surface patrolling and occasional bursts of speed.

They do best in groups. Solo fish tend to skulk and spook, and they never show their normal behavior. In a group, they establish a pecking order and relax.

• Good tankmates: other brackish species that stay mid/bottom and are not fin-nippy (figure 8 puffers are usually a bad idea), bumblebee gobies, knight gobies (size-dependent), mollies, some monos/scats in bigger tanks
• Avoid: fin nippers, hyper-aggressive fish, and anything small enough to be swallowed (they will take advantage of tiny surface fish and fry)
• Also avoid: slow surface feeders that will be outcompeted and stressed

They are not usually bullies, but they are built like little spears. If the tank is cramped, they will bump into each other and into the glass, and that is when you start seeing mouth damage and infections.

Breeding tips

Breeding Zenarchopterus in the home aquarium is doable but not common. They are livebearers (halfbeaks), and the females drop fairly large, well-formed fry when things line up. The tricky part is getting adults settled, well fed, and not stressed by tankmates or constant chasing.

• Run a species tank or very peaceful community if breeding is the goal.
• Keep them well fed with high-protein foods and some variety.
• Give heavy surface cover so females can get away from males.
• If you spot a very plump female, move her to a quiet, covered nursery tank with matched salinity and temperature.

Adults may pick off fry if they can catch them, especially in a bare tank. Dense floating cover and feeding the adults well reduces losses, but if you want numbers, raise fry separately.

Common problems to watch for

• Jumping: the #1 cause of sudden loss. Any gap is a launch ramp.
• Mouth and snout injuries: from spooking, fighting in tight quarters, or hitting the lid. These can turn into bacterial infections in brackish tanks if water quality slips.
• Slow starvation: they can look "fine" while steadily losing weight if they never really take prepared foods or if tankmates steal everything.
• Salinity swings: topping off with saltwater instead of fresh (or big water changes with mismatched SG) stresses them fast.
• External parasites and fin rot after shipping: common on new fish, especially if they were held in the wrong salinity before you bought them.

If yours are pacing the glass, clamping fins, or spooking at every movement in the room, take a hard look at the top of the tank. Add surface cover, dim the lights a bit, and check that flow is not blasting them into a corner. Those small changes make a bigger difference with this species than people expect.