Paperhead croaker

Where they come from

Paperhead croakers are estuary fish from New Guinea and northern Australia, with a spill into Indonesia. Think mangroves, muddy channels, and tidal creeks where the water swings from brackish after rain to nearly marine on a dry tide. Juveniles hang higher up the estuaries; bigger fish cruise the lower, saltier reaches.

Setting up their tank

They are active, sandy-bottom cruisers that appreciate room and steady, salty water. A single juvenile can start in a 55 gallon, but an adult needs a 5-foot tank (100-125 gallons) with plenty of open floor. Keep the layout simple: fine sand, a few smooth roots or PVC arches for shade, and long stretches to swim.

• Salinity: SG 1.005-1.012 for small juveniles, work up to 1.015-1.020 as they grow. Adults handle near-marine fine.
• Temperature: 75-82 F (24-28 C).
• pH: 7.6-8.2, moderately hard water.
• Flow and oxygen: moderate current with strong aeration. They hate stale water.
• Filtration: aim for 6-8x tank volume per hour. Canister + powerhead works well. A skimmer starts helping once SG is above ~1.015.
• Water changes: 25-35% weekly on a consistent schedule.

Use marine salt mix, not freshwater aquarium salt. Fine sand is a must. They nose around constantly, and sharp gravel will rub their snout raw. Keep lighting on the dimmer side or add shaded areas so they do not spook as much.

What to feed them

They are meat eaters with big mouths. Mine took to chopped prawn right away and learned pellets within two weeks. Start with meaty foods and sneak in quality sinking carnivore pellets once they are confident.

• Staples: chopped shrimp, squid strips, mussel, clam, tilapia, earthworms.
• Prepared: high-protein sinking pellets (New Life Spectrum, NorthFin, Hikari Carnivore type).
• Treats: live or frozen mysis, krill, sandworms. Go easy on feeders and fatty fish.

Feed juveniles small portions twice a day. Subadults and adults do well with one solid feeding 5 days a week. Rotate foods and add a vitamin soak once or twice a week to avoid gaps.

How they behave and who they get along with

Temperament is calm but predatory. They are not bullies, but anything bite-sized is food. They spook at sudden movement, then settle and resume patrolling the bottom. One can be kept alone; a small group of 3 spreads out the nerves if the tank is big.

• Good company: larger archerfish, scats, monos, big sleeper gobies, Colombian shark catfish, robust mollies in higher salinity.
• Use caution: boisterous cichlids can stress them; very pushy monos or scats will outcompete them at feeding if you do not spot-feed.
• Avoid: puffers (fin nippers), aggressive triggers if you go full marine, and any shrimp or small fish.

Breeding tips

Not a home aquarium project. Croakers are broadcast spawners with drifting larvae, and they cue off tides, temperature changes, and big open water. Sexing is not straightforward, and there are no reliable hobbyist reports of breeding this species in tanks. Enjoy them as display fish.

Common problems to watch for

Most issues come from rough substrate, dirty water, or parasites from the wild. Keep the sand smooth, oxygen high, and salinity steady. They tell you something is off by hanging near the surface or going off food.

• Gilled flukes and worms: flashing, rapid breathing. Praziquantel works well; repeat per directions.
• Ich: less common at higher salinity but still possible if you keep them near fresh. Raise SG, treat promptly.
• Snout and chin rub: caused by sharp gravel or frantic bumping. Switch to fine sand and add cover.
• Fin fray and bacterial sores: from stress or scuffles. Improve water quality, add aeration, and treat if needed.
• Feeding competition: they are methodical eaters. Spot-feed with tongs so faster fish do not starve them out.
• Salinity swings: fast changes cause gasping and stress. Match new water temp and SG closely during water changes.