River garfish (halfbeak)

Where they come from

Zenarchopterus clarus is one of the halfbeaks people lump under "river garfish." In the wild they hang near the surface in calm coastal waters, river mouths, and mangroves where fresh and salt water mix. They are built for that top inch of water - long lower jaw, quick darts, always watching for tiny prey.

Setting up their tank

Think "surface fish first." They do not care about your fancy rockwork if the top is a choppy mess or they are stressed by reflections. Give them a long tank with lots of uninterrupted swimming room, calmer flow up top, and a lid that fits like it was glued on.

• Tank size: I would not keep a group in less than a 4 foot tank. Bigger is way easier with these.
• Group size: 6+ if you can. Singles and pairs get twitchy and one fish often becomes the punching bag.
• Cover: Tight lid and block every gap around plumbing. Halfbeaks jump like they get paid for it.
• Surface: Leave open water, but add floating cover (fake plants, floating macro, or even a strip of floating rings) so they feel secure.
• Flow: Strong filtration is fine, just break up surface blast. Aim returns along the back wall or use a spray bar to avoid constant surface turbulence.
• Lighting: Not too bright at the surface. Dimmer lights or floaters reduce spooking and glass surfing.
• Salinity: If you are keeping them marine, raise salinity gradually. Sudden moves are where people lose them.

I like a simple layout: sand, some rock or wood kept low, and most structure pushed to the sides so the middle and the whole surface stays open. They spend 90% of their time in the top third, so build for that.

What to feed them

Feeding is the make-or-break part. Halfbeaks are surface hunters and many arrive used to live foods. Once they recognize you as "food person" they get bold, but the first couple weeks can be touchy.

• Best starters: live or freshly killed foods near the surface (enriched adult brine shrimp, mysis, small ghost shrimp, chopped prawn, blackworms where legal).
• Frozen staples: mysis, chopped krill, finely chopped clam, quality marine blends. Thaw and offer at the surface with a turkey baster.
• Dry foods: some learn to take small floating pellets or flakes, but do not count on it at first. Train slowly by mixing with frozen.
• Feeding style: small meals 2-3 times a day beats one big dump. They are built for picking all day.

How they behave and who they get along with

They are alert, skittish, and fast. Most of their "drama" is at the surface: chasing, pecking, and little dominance spats. In a big enough group, that spreads out and you get a cool, cruising school instead of one stressed fish.

• Good tankmates: calm marine/brackish fish that stay mid to lower levels and will not steal every bite at the surface.
• Avoid: aggressive surface feeders (some damsels, dottybacks), fast boisterous eaters that outcompete them, and anything large enough to view them as snacks.
• Also avoid: fin nippers. Halfbeaks have delicate fins and they get ragged fast in the wrong crowd.

One more thing: their beak gets damaged more easily than people think. Rough netting, chasing them around, or letting them panic into hard decor can leave them with a bent or scraped jaw. After that, feeding gets harder.

Breeding tips

Breeding Zenarchopterus in home aquariums is uncommon, and I would treat it as a "nice surprise" goal rather than a plan. Many halfbeaks are livebearers (or have very advanced eggs), and you will often just notice a tiny, needle-like youngster at the surface one day if things line up.

• Keep a well-fed group with both sexes and lots of surface cover so females are not constantly harassed.
• Feed heavy on small meaty foods and keep water quality steady. Sudden salinity swings tend to shut them down.
• If you spot fry: move the adults or move the fry. Adults will pick them off, especially at feeding time.
• First foods for fry: newly hatched brine shrimp, copepods, and other tiny live foods offered at the surface.

Common problems to watch for

Most losses come from three things: jumping, refusing food after import, and slow decline from stress or poor water stability. They can look fine right up until they do not.

• Jumping: the number one killer. Fix the lid before you buy the fish.
• Starvation: new fish may ignore frozen. Start with live foods, then wean onto frozen once they are eating with confidence.
• Beak injuries: caused by panic dashes, rough handling, or hard decor near the surface.
• External parasites: flashing, clamped fins, rapid breathing. Quarantine helps a lot, but choose meds carefully if you are running marine inverts.
• Wasting while still "eating": often competition at the surface. Watch who is actually getting food and separate bullies if needed.
• Surface film and low oxygen: they live at the top, so oily films and poor gas exchange hit them first.