Roundtail duckbill

Where they come from

Roundtail duckbills (Bembrops greyae) are one of those oddball marine predators that show up from deeper coastal waters. Think dimmer light, cooler and more stable conditions, and a life built around ambushing whatever swims too close. They are not a typical reef fish, and they do not act like one either.

Setting up their tank

Give them space and calm. I have had the best luck treating them like a sit-and-wait predator that wants cover, low stress, and steady water. They spend a lot of time perched or resting, then explode into motion when food shows up.

• Tank size: bigger is better. I would not bother under 125 gallons, and 180+ makes life easier.
• Aquascape: open sand or low rock with lanes to cruise, plus a few caves or overhangs to park under.
• Flow: moderate. You want oxygenation, but not a constant sandstorm blasting their face.
• Lighting: they do fine in subdued lighting. If you run reef-bright lights, give them shaded zones.
• Cover: tight lid. They can launch when startled, especially during feeding.

Stability matters more than chasing numbers. Keep salinity steady, keep ammonia and nitrite at zero, and do not let nitrate creep into "old tank soup" territory. These fish are less forgiving of sloppy maintenance than your average hardy community marine fish.

What to feed them

They are predators, and they want meaty foods. The trick is getting them onto prepared frozen instead of depending on live feeders. Once they recognize tongs as the dinner bell, feeding gets a lot less stressful.

• Best staples: thawed silversides, chunks of marine fish, squid, octopus, and shrimp (as a mix, not the only food).
• Good variety: clam, scallop, and other marine shellfish meat in small chunks.
• Avoid: freshwater feeder fish. It is a nutrition mess long-term and brings disease risk.
• Feeding schedule: smaller portions 2-3 times a week beats one huge binge that pollutes the tank.

How they behave and who they get along with

Most of the time they look lazy, then suddenly they are not. They are not usually a nonstop bully, but they are absolutely opportunistic. Anything small enough gets treated like a snack, and slow fish that hover near their face are asking for trouble.

• Good tankmates: larger, confident fish that do not fit in their mouth and are not fin-nippers.
• Bad tankmates: tiny fish, ornamental shrimp/crabs, and aggressive pickers that stress them out.
• Risky: long-finned slow movers (they can get mouthed), and overly boisterous feeders that outcompete them.

Feeding time is where most drama happens. If you keep them with other predators, target feed the duckbill first or at least distract the others. A duckbill that misses meals tends to get bolder about "sampling" tankmates.

Breeding tips

Breeding this species in home aquariums is basically a long shot. They come from deeper-water habits, and even if you ended up with a male and female, getting natural courtship, spawning, and larval rearing going is not something most hobbyists can realistically pull off.

Common problems to watch for

Most losses trace back to three things: stress from a chaotic tank, refusing food (or only taking junk food), and shipping damage leading to infections. These are not forgiving fish, so you want to catch issues early.

• Not eating: often tied to bright lights, too much activity, or being outcompeted. Dim the tank, add cover, and try tong-feeding at the same spot.
• Mouth injuries: they can bash their snout on rock or glass during startled dashes. Give them clear swimming lanes and reduce sudden light changes.
• Parasites and bacterial issues after purchase: quarantine if you can, and do not rush them into a busy display.
• Water quality swings: big salinity or temperature shifts hit them hard. Top off consistently and do smaller, steady water changes.