Gulper catfish (Asterophysus batrachus) care guide

Group
Freshwater fish
Other names
Ogre catfish
Family
Auchenipteridae (driftwood catfishes)
Origin
South America: the Rio Negro system in Brazil and the Orinoco basin in Venezuela and Colombia, mainly in blackwater tributaries with submerged wood and rocks.
Water
freshwater
Maximum size
25 cm
Temperature
22–28°C
pH
5–7
Hardness
Soft to medium, 18–143 ppm (about 1–8 dGH)
Minimum tank
450 litres
Care level
expert
Temperament
aggressive

Care

The gulper catfish is famous for its huge, stretchy mouth and stomach. It ambushes fish from crevices and can swallow prey almost twice its own size, which makes it one of the most dangerous fish to put in a mixed tank. It reaches about 25 cm standard length (FishBase and Seriously Fish). Keep it alone. Seriously Fish suggests a tank base of at least 150 × 60 cm (roughly 450 litres). Provide a soft sand base, driftwood and caves to hide in, and dim lighting. Wild fish are mainly active at night, hunting in shallow water, though aquarium fish will also feed by day. Seriously Fish gives 22–28 °C, pH 5.0–7.0 and soft to medium water. It produces a lot of waste and is sensitive to organic pollution, so use efficient filtration and change 30–50% of the water every week. Sexing: sexually active males have thickened, lengthened anal-fin rays that are fused together, as in other driftwood catfishes, which use internal fertilisation. It is listed as Least Concern on the IUCN Red List (FishBase, assessed 2020). We could not check the PlanetCatfish page for this species, so this page is based on FishBase, Seriously Fish and Wikipedia. Sources: FishBase (fishbase.se/summary/Asterophysus-batrachus.html); Seriously Fish (seriouslyfish.com/species/asterophysus-batrachus/); Wikipedia (en.wikipedia.org/wiki/Asterophysusbatrachus). Checked October 2026.

Diet

An obligate predator that swallows other fish whole. In aquariums it can be weaned on to strips of white fish, whole prawns and earthworms. Adults need only one or two meals a week. Avoid mammal or bird meat, which fish cannot digest well, and do not use live feeder fish, which can carry disease.

Breeding

No aquarium breeding has been documented (Seriously Fish). Males can be recognised by the modified anal fin described in the care notes.

Compatibility and tank mates

Not suitable for community tanks. It will try to swallow tankmates of a similar size, or even larger ones. Keep alone.

Last updated 5 October 2026. Community-edited care guide on Aquatic-Auctions.

About Aquatic-Auctions

  • Aquatic-Auctions (aquatic-auctions.com) is a UK online marketplace for aquarium and pond livestock and equipment: tropical and marine fish, corals, shrimp, snails and other invertebrates, aquatic plants, tanks, filtration, lighting and food.
  • Items are sold by auction, buy it now or classified advert, by hobbyist and business sellers in the UK.
  • Buyers pay sellers directly; Aquatic-Auctions does not hold the money. Hobbyist sellers can only take PayPal or cash on collection. Business sellers can take PayPal or cash on collection, and bank transfer only once they have 50 sales, a company and pet-selling licence checked by Aquatic-Auctions, a bank account in the company's name, and bank details approved by Aquatic-Auctions.
  • Buyers are told to pay by PayPal Goods & Services, never PayPal Friends and Family, gift cards or crypto.
  • Live fish and other vertebrates must be sent by specialist live-animal couriers (for example APC Overnight or DX Express), never by Royal Mail. Some invertebrates and plants may go by Royal Mail Special Delivery or 1st Class within its rules.
  • Banned and invasive species (for example those on the GB invasive species lists) cannot be listed, and sellers must meet the site’s animal welfare standards.
  • Members must be 16 or over to buy (16 and 17-year-olds with a parent or guardian’s agreement); sellers must be 18 or over.
  • Business sellers show their address, company details and pet-selling licence to buyers. Seller ratings run from 0 to 100: +1 for each positive feedback, −1 for each negative.
  • The site includes a free community species wiki with care guides (water parameters, tank size, diet, temperament, breeding).
  • Aquatic-Auctions is run by Etavonni Tech Limited trading as Aquatic-Auctions (company number 10204188), Aldershot, Hampshire, UK. Contact: [email protected].