One-Spot Synodontis (Synodontis notatus)

Choose a bold Synodontis that shows itself by day

The One-Spot Synodontis (Synodontis notatus) is a large squeaker catfish from the Congo River basin. FishBase records it throughout the basin, including Pool Malebo and the drainages of the Kasai and Ubangi, in both the Democratic Republic of the Congo and the Republic of the Congo. Most fish carry one big dark spot on each silvery-grey flank, which gives the One-Spot Synodontis its name.

What sets it apart from many of its relatives is its timetable. Seriously Fish describes it as far more active by day than many Synodontis, so it makes a good catfish for a tank of lively, robust fish where you actually want to see the catfish. In return it grows large, at 25 cm or more, and it needs a big aquarium and companions it cannot swallow.

Check the names on the label

The Latin notatus means marked. ScotCat notes that it refers to the one to four blackish spots on the sides, usually one. Browse our other Synodontis squeakers, such as the Large-Spot Synodontis, to compare patterns.

Know exactly what you receive

One purchase supplies one live One-Spot Synodontis. The size option is "Standard": the fish is sent at the size currently available, 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. ScotCat describes a grey-brown to olive back with a gold sheen around the gill cover in healthy fish and a whitish underside. The number of spots varies more than the name suggests, which the next section explains.

Read the spots before you judge the fish

• Usually one spot per side: Planet Catfish and ScotCat say most fish have a single large spot, about the size of the eye, behind the dorsal fin.
• Sometimes more, sometimes none: some fish have two or more spots or none at all, and the two sides of one fish need not match.
• Regional forms: Seriously Fish lists forms with three, six or twelve spots, some sold under the invalid name S. ocellata.
• Spots stay small: ScotCat notes that juveniles have very large spots that do not grow with the body, so they look smaller on adults.

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

Plan the aquarium around a 25 cm adult

The published sizes are close but not identical. Seriously Fish gives 275 mm standard length, Planet Catfish 265 mm standard length, FishBase 26.5 cm total length and ScotCat 23 cm. Standard length stops at the base of the tail, so a fish at the top of that range is longer still. Plan for a heavy-bodied catfish of 25 cm or more.

Seriously Fish recommends a base of at least 120 × 30 cm, roughly 108 litres, and Planet Catfish agrees that an adult needs a tank of at least 120 cm. Treat that as the minimum for one fish on its own. With other large fish, or if you hope to keep more than one Synodontis, go longer and deeper.

Run a three-step space check

1. Measure the base: at least 120 cm long and 30 cm front to back; 45 cm or more front to back gives a large catfish room to turn.
2. Count the large fish: add up the adult sizes of everything you plan to keep, and check the mix with our stocking calculator.
3. Plan for growth: a young fish looks lost in a 120 cm tank, but buy the tank for the adult, not the arrival.

Place the aquarium away from radiators, windows and draughts, as OATA's catfish care sheet recommends, and use a heater all year round. Fit a secure lid: a large, active catfish can push loose cover glass aside.

Arrange caves with open swimming space

Seriously Fish recommends a dimly lit aquarium with a soft substrate and rocks, driftwood and twisted roots arranged into hiding places, plus floating plants to diffuse the light. It adds that planting is welcome but not essential, because this species often swims in midwater. Planet Catfish suggests caves made from pipes, rocks or bogwood, with an area of open swimming space as well.

Divide the footprint by function

Use smooth sand or fine gravel; OATA notes that catfish barbels are sensitive and need a soft bottom. Stand heavy rocks on the glass before adding sand, because a large Synodontis will dig under anything it can move.

Set water values inside the species range

Planet Catfish describes it as not a delicate species that tolerates most water conditions. The figures differ slightly between sources: Seriously Fish gives 22–25°C, pH 6.5–7.5 and 8–18 dGH; Planet Catfish and FishBase give 22–26°C, pH 6.0–7.5 and 4–15 dGH; ScotCat gives 22–26°C and pH 6.5–7.2. The values below sit inside all of them.

Match your tap water to the range

The ammonia, nitrite and nitrate limits are OATA's. Much of the UK has moderately hard tap water, which suits this fish once it is treated with a conditioner to remove chlorine or chloramine. Some UK supplies are very soft and may sit below 8 dGH, so check your water company's figures, compare them with our water matcher, and read our water chemistry guide before adjusting anything.

Filter for a large, hungry catfish

A 25 cm omnivore that eats meaty foods produces a lot of waste. For a 108-litre tank, Seriously Fish suggests a filter turning the water over four to five times an hour, which it puts at 430–540 litres per hour, and a heater of roughly 75–100 W in a room at about 20°C. Larger tanks need proportionally more.

Follow a weekly maintenance sequence

1. Test ammonia, nitrite and nitrate before you start.
2. Change at least 25% of the water, the weekly figure OATA recommends; heavily stocked tanks of large fish may need more.
3. Siphon the sand in front of each cave and under the wood.
4. Clean the filter pre-filter or sponge in removed tank water, never under the tap.
5. Check the heater against a separate thermometer.

Add fish gradually so that the filter bacteria keep pace; OATA explains that stocking too quickly causes "new tank syndrome". Large fish make water problems worse faster, so keep testing even when the water looks clear.

Feed a measured omnivore diet

Synodontis are omnivorous and unfussy, Seriously Fish says, taking frozen, live and dried foods and rasping at vegetable matter such as shelled peas and cucumber with the teeth in the lower jaw. Planet Catfish adds that bloodworm, shrimp and chopped cockle make it grow quickly and put on weight, while a sinking catfish pellet will do day to day.

Build one measured meal

• Staple: a sinking catfish pellet sized for the fish's mouth.
• Meaty food: thawed bloodworm, shrimp or a little chopped cockle two or three times a week.
• Greens: a few shelled peas or a slice of cucumber once a week.
• Portion: what it clears in a few minutes, once a day, as OATA advises for catfish.
• Check: remove leftovers; rich foods foul the water quickly.

Because it is active by day, it usually feeds alongside the other fish rather than waiting for darkness. If faster fish beat it to the food, add a second portion near its cave after the lights go out.

Introduce it calmly to a mature aquarium

Add it only to a mature, filtered aquarium with zero ammonia and nitrite. OATA recommends double-bagging catfish because their spines can pierce a bag, and acclimatising in a darkened room: float the sealed bag for about 10 minutes, add small amounts of aquarium water to it over up to 20 minutes, then release the fish with as little bag water as possible. Our step-by-step acclimatisation guide covers each stage.

Use a first-week checkpoint plan

A newly arrived fish may hide for a few days before showing the daytime activity the species is known for. Rapid breathing, hanging at the surface or lying on its side are signs to test the water at once.

Choose robust companions it cannot eat

Seriously Fish says it should not share a tank with any fish small enough to be eaten, and is not recommended for a general community because of its adult size. Its suggested companions are alestiid African tetras, robust cichlids (especially West African species), Ctenopoma, mormyrids, knifefish, gouramis and the larger rasboras and barbs. Its daytime activity makes it a good fit for tanks of boisterous fish.

Screen each tank mate

Decide whether to keep one or more

This is where the sources disagree. Seriously Fish says it may become territorial as it matures, especially towards other Synodontis, and is particularly aggressive towards its own species, so only one should be kept unless the tank is very large. Planet Catfish describes it as peaceful despite its size and tolerant of other catfish and of its own kind, and ScotCat calls it quite well behaved if it has room. We recommend one per aquarium, or a cave each in a tank well over 120 cm if you want more. Other large Synodontis to compare include the Angel Squeaker and the Featherfin Synodontis. Check your plan with our tank mates checker, read our cichlid care guide if you are pairing it with West African cichlids, and browse catfish and plecos, other African catfish or more centrepiece fish.

Tell it apart from look-alike squeakers

Seriously Fish warns that similar species such as S. nummifer and S. congicus are often imported with it and all sold as notata. They need the same care, but if you want the true species, ScotCat lists the features that matter. Spot count is not one of them, because it varies in all three.

Compare three features

ScotCat adds that the bony shoulder process is too similar in all three to separate them, especially in juveniles.

Handle the spines and watch for problems

OATA warns that most catfish carry spines on the pectoral fins and just behind the gills. A Synodontis locks its serrated dorsal and pectoral spines upright when alarmed, and they snag nets easily, so guide it into a container when you must move it. Healthy fish, OATA says, have clear eyes, undamaged fins, no ulcers or bumps, normal swimming and steady breathing.

Pair each sign with an action

Understand what is known about breeding

Seriously Fish, Planet Catfish and ScotCat all list it as unbred in home aquariums, although Seriously Fish mentions reports of commercial breeding projects. In the wild it breeds in seasonally flooded areas rich in tiny food organisms; it scatters its eggs and gives no parental care. Seriously Fish says adult females are much plumper than males, and that experienced keepers can sex adults by the genital papilla, though most Synodontis take two years or more to mature.

Answer One-Spot Synodontis buying questions

What is a One-Spot Synodontis?

It is Synodontis notatus, a large squeaker catfish (family Mochokidae) from the Congo River basin in the Democratic Republic of the Congo and the Republic of the Congo. It is also sold as the Domino Syno or One-spot Squeaker, and older labels spell it Synodontis notata.

Does every One-Spot Synodontis have one spot?

No. Most have one large dark spot on each flank, but some have two or more, some have none, and the two sides of one fish may differ. Seriously Fish notes regional forms with three, six or twelve spots. The spots do not grow with the fish, so they look smaller on adults.

How big does Synodontis notatus grow?

Seriously Fish gives 275 mm standard length, Planet Catfish 265 mm and FishBase 26.5 cm total length. Plan for a fish of 25 cm or more.

What size aquarium does it need?

At least a 120 × 30 cm base, about 108 litres, according to Seriously Fish; Planet Catfish also says an adult needs a tank of at least 120 cm. More space is better for a fish of this size.

Can I keep more than one?

The sources disagree. Seriously Fish says it is particularly aggressive towards its own species and only one should be kept unless the tank is very large, while Planet Catfish describes it as tolerant of its own kind. We recommend one per aquarium unless the tank is well over 120 cm and has a cave for each fish.

What water conditions does it need?

Seriously Fish gives 22–25°C, pH 6.5–7.5 and 8–18 dGH; Planet Catfish and FishBase give 22–26°C, pH 6.0–7.5 and 4–15 dGH. We suggest 23–25°C, pH 6.5–7.5 and 8–15 dGH, which satisfies all of them.

Is it active during the day?

More than most Synodontis. Seriously Fish describes it as far more diurnal than many species, which makes it a good catfish for a tank of boisterous fish where you want to see it.

What does it eat?

It is an unfussy omnivore. Give a sinking catfish pellet as the staple, with frozen bloodworm, shrimp or chopped cockle and some vegetable food such as shelled peas or cucumber.

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

• Seriously Fish: Synodontis notatus — size, aquarium base, water range, aquarium layout, diet, compatibility, sexing and the regional spot variants.
• Planet Catfish: Synodontis notatus — names, synonyms, size, spot variation, water range, feeding, furniture and compatibility.
• FishBase: Synodontis notatus — classification, distribution, maximum length and water range.
• ScotCat factsheet: Synodontis notatus (February 2014) — how to separate S. notatus from S. congicus and S. nummifer, colour, care and diet.
• 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.