Monte's croaker
Plagioscion montei
Monte's croaker features a slender body with a silvery-blue hue and distinctive dark spots along its lateral line.
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About the Monte's croaker
Plagioscion montei is a freshwater croaker from the Amazon basin (Brazil and Peru) that grows into a sleek, silvery predator with that classic Sciaenidae shape. Its whole family is famous for making croaking/drumming sounds (swim bladder stuff), so its close relatives are pretty fun fish behavior-wise even if this exact species is rarely seen in the aquarium trade.
Also known as
Quick Facts
Size
34 cm SL
Temperament
Semi-aggressive
Difficulty
Advanced
Min Tank Size
180 gallons
Lifespan
8-12 years
Origin
South America
Diet
Carnivore/piscivore - meaty frozen foods, shrimp, fish-based chunks, quality predator pellets
Water Parameters
24-30°C
5.5-7.5
1-12 dGH
Need a heater for this species?
This species needs 24-30°C in a 180 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it a long tank, not a tall one - they cruise and spook easily. Think 6 ft footprint if you want an adult to look relaxed, with open water and a few chunky pieces of wood for cover.
- They are freshwater but hate dirty water; keep ammonia/nitrite at 0 and nitrates low with big weekly water changes and heavy filtration. Keep temp around 75-82F and aim for neutral-ish water (about pH 6.5-7.5) with decent oxygen and flow.
- They are a predator with a big mouth, so anything that fits will vanish at night. Avoid small dithers and livebearers unless you like feeding expensive snacks.
- Feed after lights dim because they hunt better then; start with meaty frozen like shrimp, silversides, krill, and chopped fish, and train onto sinking carnivore pellets. Skip feeder goldfish - they bring parasites and fatty liver issues.
- Tankmates need to be robust and too big to swallow: larger characins, big catfish, and similar-sized cichlids can work if the tank is huge. Avoid fin-nippers and hyper cichlids that will keep it pinned in a corner.
- Use sand or smooth fine gravel and keep decor snag-free - they can bolt and scrape their face and flanks on sharp rocks. A tight lid is non-negotiable because they jump when startled.
- Watch for mouth and gill damage from ramming glass (usually from sudden lights-on or people walking up fast), and for skinny belly despite eating (often internal parasites). Quarantine new fish and deworm if you see stringy white poop or weight loss.
Compatibility
Good Tankmates
- Other medium-to-large South American cichlids that can hold their own (severums, blue acara, festiva types) - not the tiny stuff. Monte's croaker is semi-aggressive and predatory, so you want tankmates that are too big to be food and not total jerks.
- Sturdy schooling fish that get some size and stay fast (silver dollars, larger characins like bigger headstanders) - they do better in groups and they are not easy targets.
- Armored bottom crew that keeps to themselves (medium/large plecos, Panaque, big Hypostomus) - they are tough enough to ignore the croaker's attitude and mostly run different real estate.
- Big, chill catfish (Synodontis in a big tank, or larger Doradid 'talking' catfish) - they are usually unbothered by the croaker and are not shaped like an easy snack.
- Other robust, similar-sized oddballs in a roomy setup (datnoids, larger freshwater eels like spiny eels) - works best when everybody is well-fed and you have lots of cover so nobody gets singled out.
Avoid
- Small community fish (neon/cardinal tetras, guppies, small barbs) - if it fits in the croaker's mouth it is basically live food, and they get picked off over time even if it looks 'fine' at first.
- Slow, fancy-finned fish (angelfish longfins, fancy goldfish, bettas) - the croaker will harass them, and the slow movers just cannot get away from the chasing.
- Hyper-nippy or super-territorial bruisers (red devils, jaguars, mature Midas types) - they do not 'teach him a lesson', they just turn the tank into a nonstop war zone.
Where they come from
Monte's croaker (Plagioscion montei) is a South American freshwater sciaenid. Think big river systems with moving water, seasonal swings, and lots of baitfish. They are built for hunting in open water and along edges, not for picking at plants all day.
If you have kept marine croakers/drums before, the vibe is similar: they are predatory, a bit spooky at first, and they like room to cruise. Just in freshwater.
Setting up their tank
This is an advanced fish mostly because of adult size, appetite, and the amount of waste they produce. Give them space first, then worry about decor.
- Tank size: the bigger the better. For an adult, I would not bother with anything under 180 gallons, and 240+ is where it starts feeling comfortable.
- Footprint matters more than height. Long tanks let them glide and turn without bashing their face.
- Filtration: think overbuilt. Large canisters or a sump with lots of biological media, plus serious mechanical filtration for the mess.
- Flow and oxygen: they appreciate steady current and high dissolved oxygen. Add powerheads/wavemakers aimed along the back wall and plenty of surface agitation.
- Substrate: sand or fine gravel works. Keep it simple and easy to siphon.
- Hardscape: big driftwood pieces and a few rock piles to break lines of sight. Leave open swimming lanes.
- Lighting: moderate. Too bright and they stay jumpy; a darker background helps.
- Lid: tight-fitting. They can launch when startled, especially at night.
Plan your maintenance around the fish, not the other way around. These guys eat like predators and poop like it. If you hate big water changes, pick a different species.
Water parameters are less about chasing a magic number and more about stability and cleanliness. Neutral-ish to slightly acidic is fine, warm tropical temps are fine, but ammonia and nitrite have to stay at zero and nitrates should not be allowed to creep into the "my eyes burn" zone. You will know when you are under-filtered because the water starts looking tired fast.
What to feed them
They are fish-eaters by nature, and they act like it. Most new imports want moving food. Once they settle, you can usually convert them to frozen and prepared foods, but it takes patience and a bit of strategy.
- Best staples: frozen/thawed smelt, silversides, sardine chunks, white fish fillet, shrimp, squid, and good carnivore pellets once they accept them.
- Good variety: earthworms, large insect larvae, and occasional mussel or clam meat for a change.
- How I get them onto pellets: feed frozen first, then start mixing in sinking carnivore pellets during a feeding response. Use tongs or a feeding stick if they are shy.
- Feeding schedule: juveniles can eat smaller meals most days. Adults do better with larger meals 2-4 times a week. Overfeeding turns into water quality problems fast.
Avoid feeder goldfish/rosy reds. Besides the disease risk, long-term use brings nutritional issues (thiaminase in some feeder fish). If you want "live" as a tool, use quarantined livebearers you raised yourself or, better yet, use live worms/insects to trigger feeding.
Watch the body shape from above. A healthy fish looks solid and muscular, not pinched behind the head. If they start getting thick in the belly and sluggish, cut back and increase water changes.
How they behave and who they get along with
Monte's croaker is a predator with a pretty calm cruising style. They are not usually fin-nippers, but anything that fits in the mouth is on the menu, and they can inhale prey that surprises you.
- Temperament: generally not a brawler, but confident once settled.
- Activity: more active at dusk/night. They may hide or freeze when the room is busy, especially early on.
- Tankmates: choose large, sturdy fish that do not look like food. Big characins, larger cichlids with similar temperament, and robust catfish can work in a big tank.
- Avoid: small tetras, small catfish, slow fancy fish, and anything narrow-bodied that screams "baitfish."
- Group vs solo: a single specimen is common. Multiple can work only with a very large tank and careful sizing so one does not dominate feeding.
They settle in faster if you give them a dark background, floating cover (even a strip of floating plants), and predictable routines. Same time feeding, same approach to the tank. Sudden movement spooks them.
Breeding tips
Breeding in home aquariums is rare. Most folks keep them as showcase predators, and the hurdles are real: you need a big group, lots of space, and seasonal cues. In the wild, many river predators respond to rainy season changes (fresh influx, temp shifts, current changes).
If you ever try it: think "pond or monster tank" and conditioning with heavy, varied foods. Simulating seasonal change with gradual temperature adjustments and big, frequent water changes can sometimes trigger spawning behavior in river fish, but do not buy this species expecting to breed it.
Common problems to watch for
- Not eating after purchase: very common. Dim the lights, give hiding cover, keep the tank quiet, and start with enticing foods like worms or moving frozen on a feeding stick. Do not panic-medicate.
- Jumping and collisions: they spook and bolt. Use a lid, avoid sudden light changes, and keep hardscape away from their main cruising lane.
- Water quality slide: big meals equal big waste. Cloudy water, oily surface film, and rising nitrates mean you need more mechanical filtration, more bio capacity, and bigger water changes.
- Internal parasites: wild fish can come in thin and stay thin despite eating. Quarantine if you can, and consider deworming protocols used by experienced keepers (species-safe meds, correct dosing).
- Mouth damage: from slamming into glass or decor. Reduce stress triggers and keep the layout open.
- Ich/velvet after stress: they can show spots after shipping or a temperature swing. Stable temp, strong aeration, and prompt treatment in quarantine beats nuking the display tank.
The biggest "problem" with Monte's croaker is underestimating adult size and feeding impact. If you build the tank around easy cleaning and heavy filtration from day one, the fish is a lot more enjoyable.
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