Giant Upside-Down Catfish (Synodontis batensoda)

Choose a giant upside-down catfish for a large aquarium

The Giant Upside-Down Catfish (Synodontis batensoda) is a squeaker catfish that spends almost its whole life swimming belly-up. Planet Catfish notes that, like the much smaller S. nigriventris, it almost always swims inverted, and its colours match the habit: FishBase describes a reversed pattern, with a light grey back and a black belly, so the fish is camouflaged whichever way up you see it.

It is a fish of the Nile and the great West African rivers. FishBase lists the Nile, Senegal, Gambia, upper Volta, Ogun, Osse, Niger (including the Bénoué) and Chad basins, and Planet Catfish says it lives in slow-flowing pools and marshes beside large rivers. It grows much larger than the upside-down catfish most shops sell, to about 28 cm, so it is a fish for a big, calm aquarium.

Check the names on the label

The species name comes from schal baten soda, a local name in Cairo that ScotCat translates as "the squeaker with the black belly". Its genus has moved back and forth: Bleeker created Brachysynodontis for it in 1862 because of its gill rakers and the lack of a gap between the dorsal and adipose fins, and a 2010 study of its skeleton, cited by Planet Catfish, returned it to Synodontis. ScotCat adds that this is the fish chosen in 1973 as the emblem of the former Catfish Association of Great Britain.

Compare the three upside-down catfish we sell

Three different Synodontis are sold as "upside-down catfish", and they are not interchangeable. We also sell the Black Upside-Down Catfish (S. nigriventris) and the False Upside-Down Catfish (S. nigrita). The table sets out how they differ, so you can be sure which one suits your tank.

Check size, swimming habit and markings

In short: choose S. nigriventris for a small community aquarium, and S. batensoda only if you have room for a fish nearly three times as long. The large adipose fin and compressed body are thought to help S. batensoda stay stable while inverted, according to Planet Catfish.

Know exactly what you receive

One purchase supplies one live Giant Upside-Down Catfish at the size currently available ("Standard"), which is well below the adult size. Sex is not chosen or guaranteed. The photographs show the type of fish, not the individual you will receive.

Young fish look different from adults. ScotCat describes juveniles with large dark blotches on the flanks separated by a pale network, while adults are silver-green to blue-grey, occasionally reddish-brown, with a blackish underside, grey fins partly marked with dark spots, and black barbels. FishBase adds that the pelvic, anal and tail fins are always covered with spots in cross rows.

Plan the group before you order

• One fish: workable in a large community tank.
• A small group: closer to nature, as ScotCat reports that wild fish gather in large shoals, but only in a tank long enough for several 28 cm fish.
• With other Synodontis: choose calm species only; Planet Catfish and ScotCat both warn that more aggressive Synodontis may bully it.

Before you order, read our delivery and Live Arrival Guarantee information and make sure the aquarium is mature and large enough for the adult.

Plan the aquarium around a 28 cm adult

Sizes for this species vary more than for most fish. FishBase gives a maximum of 28.6 cm total length and 1.5 kg, but notes that one reference reports 50 cm and another only 26.5 cm. ScotCat gives 17.5 cm, and Planet Catfish lists 500 mm while noting that some sources say 270 mm. Most aquarium fish will stay well below 50 cm, but plan for about 28 cm.

No source we checked publishes a minimum tank. For the similar-sized S. notatus, Seriously Fish recommends a base of at least 120 × 30 cm, so we use that as the floor for one fish. Because this species swims in open water near the surface as well as along the bottom, a long, wide tank of 150 cm or more is the better choice for a group.

Run a three-step space check

1. Measure the base: 120 × 30 cm minimum for one fish, 150 cm or more for several.
2. Check the height: leave clear water between the top of the décor and the surface so the fish can swim inverted along the top.
3. Work out the volume: our tank volume calculator gives the litres for sizing the filter and heater.

Keep the tank away from radiators, windows and draughts, as OATA's catfish care sheet advises, and fit a tight lid.

Furnish for a fish that rests upside down

Planet Catfish recommends driftwood with horizontal branches and broad-leaved plants such as Anubias, because this fish both rests and swims inverted. It will hang beneath a branch or leaf by day. The theories for this habit are summarised on the species' Wikipedia page: it may make it easier to graze the undersides of submerged wood, and a 1994 study in the journal Copeia, cited there, links it to more efficient breathing at the oxygen-rich surface. ScotCat links it to surviving in low-oxygen pools in the dry season.

Divide the space by function

Use smooth sand or fine gravel, which OATA recommends to protect catfish barbels, and keep the lighting moderate or shaded by floating plants.

Set water values inside the species range

Planet Catfish gives 24–28°C and pH 6.4–7.8. FishBase gives 23–27°C, and ScotCat 23–27°C with pH 6.0–7.2. The targets below sit inside all of them. No hardness figure is published; wild fish live in river margins and marshes, and soft to moderately hard tap water treated with conditioner suits a hardy species like this.

Match your tap water to the range

The ammonia, nitrite and nitrate limits are OATA's. Compare your own readings with our water matcher, and see our water chemistry guide for what each one means.

Filter for a large fish and keep the surface moving

A fish of nearly 30 cm needs filtration to match. On its Synodontis pages, Seriously Fish suggests a filter turning the water over four to five times an hour; for a 150 cm tank that means a large external filter or two. Angle the outlet to ripple the surface, but leave calmer water under the branches where the fish rests. Our guide to the nitrogen cycle explains why a mature filter matters before a large fish arrives.

Follow a weekly maintenance sequence

1. Test ammonia, nitrite and nitrate.
2. Change at least 25% of the water each week, as OATA recommends.
3. Siphon under the wood and around the caves.
4. Wipe algae from the undersides of leaves only lightly; the fish rests there.
5. Rinse filter media in removed tank water, never under the tap.

OATA warns that stocking too quickly causes "new tank syndrome", because the filter bacteria cannot keep up. Add a large fish like this only to a well-established aquarium.

Feed from the surface down

In the wild it eats plankton, algae and detritus, and also takes surface insects, midge larvae, small crustaceans and molluscs, according to Planet Catfish and FishBase; its many gill rakers suit straining small food from the water. Planet Catfish says it readily accepts flake in the aquarium and enjoys brine shrimp and bloodworm as treats. ScotCat reports that it feeds by day, takes live, frozen, tablet, pellet and flake foods, and was seen gnawing courgette left for a pleco.

Build one measured meal

• Surface and midwater: good flake or small floating pellets, which it takes while swimming inverted.
• Bottom: sinking pellets or tablets for when it feeds on the substrate.
• Meaty food: thawed frozen bloodworm or brine shrimp two or three times a week.
• Greens: a slice of blanched courgette now and then.
• Portion: only what is eaten in a few minutes, once a day, as OATA advises.

Introduce it calmly to a mature aquarium

OATA recommends double-bagging catfish because their spines can pierce a bag. Acclimatise with the lights off: float the sealed bag for about 10 minutes, add small amounts of tank water over up to 20 minutes, then release the fish with as little bag water as possible. Our guide on how to acclimatise new fish gives the full method.

Use a first-week checkpoint plan

Swimming upside down is normal for this species, so do not mistake it for a swim-bladder problem. Warning signs are rapid breathing, hanging at the surface, lying on the bottom on its side, or clamped fins.

Choose calm tank mates

Planet Catfish calls it a peaceful species that poses no threat even to small fish, and warns that more aggressive Synodontis may harass it. ScotCat agrees that it is easy-going but can be bullied by more aggressive members of the family. Its tank mates therefore matter more for its sake than for theirs.

Screen each tank mate

Our kribensis guide covers a good West African cichlid companion. Check any planned mix with our tank mates tool, and browse catfish and plecos, other Synodontis catfish, the wider range of African catfish or our rare and collector fish.

Handle the spines and watch for problems

FishBase lists this species as venomous, and OATA warns that most catfish carry spines on the pectoral fins and just behind the gills. ScotCat describes a dorsal spine that ends in a filament and pectoral spines strongly serrated on the inner edge. Never hold it in your hand; guide it into a container for moving, and wash any spine wound and seek medical advice if it becomes painful or swollen.

Pair each sign with an action

Understand what is known about breeding

Planet Catfish and ScotCat both list aquarium breeding as unreported. FishBase records that the species lays eggs and pairs off to breed, and that fish mature from about 13 cm. In the wild, ScotCat notes, it moves from the main rivers into pools and marshes, possibly ahead of spawning. The IUCN lists it as Least Concern, though Wikipedia, citing the assessment, notes that it is now regionally extinct in northern Africa, where it was once found at Cairo during floods.

Answer Giant Upside-Down Catfish buying questions

What is a Giant Upside-Down Catfish?

It is Synodontis batensoda, a large squeaker catfish (family Mochokidae) from the Nile and the big West African river basins: the Senegal, Gambia, Volta, Niger and Chad. It almost always swims belly-up and has a dark belly and a light grey back, the reverse of most fish.

How is it different from the upside-down catfish we usually see?

The common upside-down catfish is Synodontis nigriventris, a Congo species of about 10 cm that lives in groups. Synodontis batensoda grows far larger, at about 26–29 cm according to FishBase, comes from West Africa and the Nile, and has an adipose fin that almost touches the dorsal fin and a broad black membrane along each upper-jaw barbel.

Is it the same fish as the False Upside-Down Catfish?

No. The False Upside-Down Catfish is Synodontis nigrita, a dark grey fish with black spots on the body and fins that swims inverted far less often. Synodontis batensoda is light grey above with a black belly, has a deeper, shorter body and swims inverted almost all the time.

How big does Synodontis batensoda grow?

Published sizes vary. FishBase gives 28.6 cm total length and notes one reference of 50 cm and another of 26.5 cm, while ScotCat gives 17.5 cm. Plan for a fish of about 28 cm.

What size aquarium does it need?

No minimum is published for this species. We use the 120 × 30 cm base recommended for the similar-sized Synodontis notatus as the floor for one fish and suggest 150 cm or more for a small group.

What water conditions does it need?

Planet Catfish gives 24–28°C and pH 6.4–7.8; FishBase and ScotCat give 23–27°C, with ScotCat suggesting pH 6.0–7.2. We suggest 24–27°C and pH 6.5–7.2.

Is it peaceful?

Yes. Planet Catfish calls it a peaceful species that poses no threat even to small fish, but more aggressive Synodontis may bully it, so choose its catfish companions carefully.

Has it been bred in aquariums?

Not that we can find. Planet Catfish and ScotCat both list aquarium breeding as unreported.

How many fish come with one purchase?

One live fish of the standard size currently available. Sex is not chosen or guaranteed.

Consult the care references

• Planet Catfish: Synodontis batensoda — names, synonyms, gill rakers, adipose fin, inverted swimming, water range, feeding, furniture and compatibility.
• FishBase: Synodontis batensoda — classification, distribution, the different maximum sizes published, diagnosis and inverted colour pattern.
• ScotCat factsheet: Synodontis batensoda (November 2001) — size, water range, wild shoaling, aquarium behaviour, diet and the meaning of the name.
• Wikipedia: Synodontis batensoda — range and regional extinction from the IUCN assessment, and the two theories for upside-down swimming, including the 1994 Copeia study by Chapman, Kaufman and Chapman.
• Seriously Fish: Synodontis nigriventris — the true upside-down catfish: size, water range, inverted behaviour and group size.
• Planet Catfish: Synodontis nigriventris — the true upside-down catfish: size, range, furniture and compatibility.
• Seriously Fish: Synodontis nigrita — the false upside-down catfish: size, aquarium base, water range, behaviour and how often it swims inverted.
• Planet Catfish: Synodontis nigrita — the false upside-down catfish: identification, size and range.
• Seriously Fish: Synodontis notatus — size, aquarium base, water range, aquarium layout, diet, compatibility, sexing and the regional spot variants.
• OATA: How to look after freshwater catfish — UK guidance on catfish water quality, spines, acclimatisation, feeding and weekly water changes.
• Tropical Fish Co delivery policy — current dispatch days and Live Arrival Guarantee terms.