Megalonema platycephalum (no established English common name)
Megalonema platycephalum
The Flathead long-whiskered catfish features a broad, flat head, long sensory whiskers, and a pale brown to yellow-green body with dark mottling.
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About the Megalonema platycephalum (no established English common name)
A long-whiskered South American catfish that tops out around a foot, with sleek lines and elegant fin filaments. Field and museum notes even list beetle larvae, fish scales, and catfish spines in its diet, which makes it a quirky predator to watch. It turns up in shops only rarely and needs real space to thrive.
Also known as
Quick Facts
Size
12 inches (30 cm)
Temperament
Semi-aggressive
Difficulty
Advanced
Min Tank Size
120 gallons
Lifespan
10-15 years
Origin
South America
Diet
Carnivore - insect larvae and fish tissues; in aquaria takes sinking pellets and frozen foods
Water Parameters
22-27°C
6-7.2
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This species needs 22-27°C in a 120 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Start with a tank of at least 120 gallons (4×2×2 ft/120×60×60 cm); this South American catfish tops out around 12 in/30 cm and needs real space.
- Run it in freshwater at 22-27 C and pH 6.0-7.2, and keep those numbers steady.
- Feed a carnivore menu: sinking catfish pellets and frozen foods such as bloodworms and pieces of fish; it naturally eats insect larvae and fish tissues.
- Choose tankmates carefully: it is semi-aggressive and will treat bite-sized fish as food, so stick to robust, similarly sized companions.
- Field records list beetle larvae, fish scales, and even catfish spines in its diet, so avoid delicate species that might invite picking or predation.
- Plan for 10-15 years of care; this is not a short-term fish.
- As a large carnivore it produces a lot of waste, so scale up filtration and water changes accordingly.
- It shows up in shops only rarely, so have the big tank and suitable foods ready before you bring one home.
- Provide strong current and highly oxygenated, clean water (riverine species); use a sand-like substrate and leave plenty of open swimming space.
Compatibility
Good Tankmates
- Large, deep-bodied characins that are too big to swallow (silver dollars, adult Metynnis/Myleus) schooling midwater
- Robust South American cichlids with moderate temperaments (oscars, severums, adult Geophagus), sized so neither sees the other as food
- Large armored bottom-dwellers that mind their own business, like big plecos and doradid talking catfish; give each plenty of caves to prevent turf clashes
- Large knifefish of similar size (black ghost knifefish) with ample cover so both species can retreat
- Big, hardy bichirs (Polypterus) or other non-nippy, bottom-oriented fishes, provided they are too bulky to be eaten and there is lots of floor space
Avoid
- Anything small enough to fit in its mouth: small tetras, rasboras, livebearers, dwarf cichlids, small catfish, shrimp
- Fin-nippers that target whiskers and fin filaments (tiger barbs, serpae tetras, some Leporinus/Anostomus)
- Very aggressive, territorial bruisers that will harass or damage barbels (large Central American cichlids like Midas/Jaguar/Dovii, or similarly pugnacious characins)
- Slow or long-finned show fish that cannot get out of the way (angelfish, discus) which risk torn fins or nighttime predation
The Flathead long-whiskered catfish (Megalonema platycephalum) is a South American freshwater predator with sleek lines, long barbels, and elegant fin filaments. It reaches about 12 inches/30 cm and can live 10-15 years. This is an advanced, space-hungry catfish that shows up in shops only rarely.
- Adult size: up to 12 in (30 cm)
- Minimum tank: 120 US gallons
- Water: freshwater; pH 6.0-7.2; 22-27 C
- Temperament: semi-aggressive, predatory
- Diet: carnivore; takes sinking pellets and frozen foods
- Care level: advanced
- Origin: South America
Origin and natural habitat
A long-whiskered South American catfish, Megalonema platycephalum is recorded in field and museum notes with a bottom-foraging diet that includes insect larvae, fish tissues and scales, and even catfish spines. Expect a benthic predator that patrols the lower levels and investigates with its barbels.
Aquarium setup and water conditions
Give this fish real room. A 120-gallon tank is the floor, and a long footprint with open swimming space plus several solid retreats (logs, large pipes, stable rockwork) works best. Keep hardscape smooth and stable so sudden dashes do not cause injuries. Use sand or fine, rounded gravel to protect the barbels, and keep lighting on the subdued side with some shaded areas.
Large carnivores produce a lot of waste, so run robust, well-oxygenated filtration and keep up with large, regular water changes. Stable, clean water is key to avoiding barbel damage and infections.
Target parameters: 22-27 C; pH 6.0-7.2.
Diet and feeding
In the wild this catfish eats insect larvae and fish tissues; gut studies even turn up beetle larvae, scales, and catfish spines. In aquaria it accepts quality sinking carnivore pellets and a rotation of meaty frozen foods. Offer modest portions and watch body condition rather than feeding by the clock.
- Staples: sinking carnivore pellets
- Frozen/thawed items: fish pieces, shrimp, bloodworms, similar fare
Drop food near its retreat so it can feed confidently, and remove uneaten items promptly to keep water quality high.
Behavior and tankmates
Semi-aggressive and strongly predatory, this species will swallow anything it can fit in its mouth and may posture with similarly sized bottom fish at feeding time. It is best kept with robust, similarly sized tankmates that are too large to be considered food and that will not nip its fin filaments.
- Avoid small fish and shrimp - they will be eaten.
- Skip fin-nippers that target barbels and fin filaments.
- Be cautious mixing with smaller catfish; predation attempts on spiny species can injure both fish.
Field records noting catfish spines in the gut underline the risk of keeping this species with smaller or similarly shaped catfish.
Common problems and how to avoid them
- Underestimating space: a foot-long, muscular catfish needs a large, uncluttered footprint and strong filtration.
- Barbel wear: rough substrate and poor water quality damage barbels; use sand/fine gravel and keep water very clean.
- Predation: do not mix with bite-sized tankmates; feed appropriately to reduce hunting interest but never rely on feeding to prevent predation.
- Injury from decor: secure heavy wood/rock and avoid sharp edges; provide wide retreats it cannot wedge into.
- Water quality swings: heavy bioload demands ample biofiltration and regular, large water changes.
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