Humphead thryssa

Where they come from

Humphead thryssa are anchovies from South and Southeast Asia. Think muddy coastal shallows, mangrove edges, and estuaries from the Bay of Bengal across to Indonesia and the Philippines. They cruise in big schools over open water, picking plankton out of the current.

Setting up their tank

These are schooling, high-oxygen, open-water fish. I would not attempt them in anything under a 6-foot tank. They are quick, nervous, and jumpy, and they get bigger than you expect for an anchovy (think 6-8 inches).

• Tank size and shape: 180+ gallons, long footprint. Open central swimming lane. Keep rockwork low and to the ends.
• Lid: Tight-fitting, full coverage. 1/4 inch mesh or smaller. Seal gaps around cables.
• Flow and oxygen: Strong, steady current across the length (not chaotic blasting). Aim 10-15x turnover and lots of surface agitation. Big skimmer helps.
• Lighting: On the dimmer side with a gentle ramp-up/ramp-down. They spook under sudden bright light.
• Background: Dark back and sides cut reflections. Nervous fish calm down when they do not see their own mirror-image school.
• Parameters: 75-80 F (24-27 C), salinity 1.022-1.025, pH 8.0-8.4, ammonia/nitrite 0, nitrate as low as you can keep it (under 20 ppm).
• Aquascape safety: Avoid sharp rock near glass. They pinball when startled. Foam edge guards on tank braces help.
• Quarantine: Use a roomy, covered QT with blacked-out sides and heavy aeration. Handle in a specimen container instead of a net.

What to feed them

Plan for frequent small feedings. They are midwater planktivores and rarely accept dry food at first. Get them eating, then worry about weaning.

• Starter foods: Live enriched adult brine shrimp, live mysis, and bottled/live copepods. Offer in low light.
• Frozen options: Mysis, calanus, finely chopped krill, shaved seafood, fish roe. Enrich with a vitamin/HUFA supplement.
• Feeding style: Broadcast into the current so it drifts midwater. Turkey baster or pipette works well.
• Frequency: 3-6 small feeds per day at first. Once settled, you can drop to 2-3, but they do better with more frequent, lighter meals.
• Weaning: Mix tiny pellets with frozen once they hit food confidently, but do not count on pellets becoming a staple.

How they behave and who they get along with

They are schooling fish. A lone Humphead thryssa is a stress case. Six is my bare minimum; eight or more feels right in a big tank. They pace in formation, then panic if startled, so give them room and predictable routines.

• Good company: Peaceful, non-nippy, small-mouthed midwater fish that will not outcompete them. Think chromis (healthy groups), scissortail and zebra dartfish, peaceful fairy/flasher wrasses, cardinals.
• Use caution: Fast anthias and tangs can hoover all the food unless you target the thryssa first.
• Avoid: Anything predatory or grabby (groupers, lionfish, hawkfish, dottybacks, large angels), and fin-nippers. Skip big anemones and very stingy corals; these fish wander into things.
• Reef note: They are reef-safe with corals in behavior, but they are accident-prone. FOWLR or very mellow reef setups are less drama.

Breeding tips

These are pelagic spawners. Realistically, you will not raise them in a home aquarium. In public aquaria, they may release eggs in the water column at dusk, eggs drift, and larvae need live plankton round-the-clock.

• If you ever see spawning behavior: Dim lights at dusk, tight schooling, quick dashes and shimmer. Skimmer and overflows will grab the eggs.
• Raising larvae would require: Kreisel/round tank, rotifers and copepods on tap, sterile technique, and lots of space. Not a weekend project.

Common problems to watch for

• Refusing food: Start with live, feed in low light, use steady current. Try smaller particle sizes and fish roe if they ignore mysis.
• Mouth and snout damage: Never net them. Use a specimen container. Pad hard edges and keep rock away from the glass.
• Jumping and glass strikes: Tight lid, gentle light ramping, dark background. Avoid slamming doors near the tank.
• Oxygen stress: Gasping at the surface or hugging the flow. Increase surface agitation, clean the skimmer, and check temperature.
• Parasites after import: Quarantine. I like a quiet QT, heavy aeration, and observation first. If treatment is needed, dose carefully and test often; these fish are sensitive to rough handling and sudden changes.
• Weight loss despite eating: Consider internal parasites. Medicated food can help, but only once they are eating reliably.
• Nutrient creep from heavy feeding: Oversized skimmer, refugium/macro, filter socks changed often, and regular water changes keep things stable.