−11%
Moderate
Cichlasoma blue jack dempsey
24–30°C · pH 6.5–8 · 250L
£28.47£31.99
The classic Jack Dempsey - a bold Central American cichlid that grows into a dark, heavily speckled 15-20cm centrepiece fish. Sold from 3-4cm to grow on. Needs space and firm tank-mate choices.
Adult size is the maximum length this species reaches at full maturity (scientific sources). The livestock you receive will be younger and smaller — pick a size variant above for the actual shipping size. Product-photo provenance and any image-specific limitations are stated on the listing.
Cichlasoma octofasciatum
Save when buying multiple fish. Each quantity is one fish; sex and pair formation are not guaranteed unless the selected variant explicitly states them.
The classic Jack Dempsey - a bold Central American cichlid that grows into a dark, heavily speckled 15-20cm centrepiece fish. Sold from 3-4cm to grow on. Needs space and firm tank-mate choices.
Adult size is the maximum length this species reaches at full maturity (scientific sources). The livestock you receive will be younger and smaller — pick a size variant above for the actual shipping size. Product-photo provenance and any image-specific limitations are stated on the listing.
Cichlids are one of the most diverse fish families in the hobby. From tiny apistogrammas to massive oscars, this guide covers the basics of keeping them well.
Maintain these water conditions for optimal health and vibrant colors
The Jack Dempsey is one of the great classic aquarium cichlids, and one of the few fish in the hobby genuinely named after a heavyweight boxer. Listed by our supplier as Cichlasoma octofasciatum and by current literature as Rocio octofasciata, the Jack Dempsey Cichlid is a bold, intelligent Central American fish that grows into a dark, heavily speckled centrepiece animal of 15 to 20 cm. It is not a community fish and it is not a beginner's first cichlid, but for anyone who wants a large fish with real personality and a ten-year life ahead of it, it is hard to beat. If you are researching jack dempsey care, working out jack dempsey tank size, or comparing large cichlids for sale UK, start here.
This listing is the standard Jack Dempsey — the wild-type fish. The Electric Blue colour form is a separate, considerably more expensive listing, and the difference is explained in full below so nobody buys the wrong one.
The Jack Dempsey is a Central American fish from the Atlantic slope, recorded from Mexico's Veracruz state through Belize and Guatemala into western Honduras — from the Río Actopan in the north down to the ríos Motagua, Chamelecón and Ulúa. Despite decades of shops filing it under "South American cichlids", it is not a South American fish.
Its natural waters are warm, slow-moving lowland habitats: canals, drainage ditches, weedy margins of rivers, swamps and pools. The substrate is typically sand or silt, often with dense marginal vegetation and plenty of submerged wood and root cover. Water is warm and generally on the harder, more alkaline side. That background explains three things about keeping them: they tolerate a very wide range of water chemistry, they expect cover and structure rather than open glass, and they are entirely comfortable rearranging the substrate to suit themselves.
A Jack Dempsey that has somewhere to claim is a calmer Jack Dempsey. Solid rockwork, bogwood and a couple of visual barriers across the tank give a territorial fish a defined patch and stop it treating the entire aquarium as its own. Bare tanks make them worse, not better.
An adult Jack Dempsey is a deep-bodied, muscular cichlid with a dark charcoal to near-black ground colour, overlaid with rows of iridescent blue, green and gold spangles that catch the light as the fish turns. Mature fish carry red or orange edging along the dorsal and caudal fins. There is usually a dark blotch on the mid-flank and another at the base of the tail.
Juveniles look nothing like this. At the 3-4 cm size fish are sold at, they are a plain grey-brown with faint barring and only a scatter of pale spots. This is the single most common disappointment among first-time buyers, and it is entirely normal. The colour builds over the first year and keeps improving as the fish matures.
Sexing: mature males grow larger, develop longer and more pointed dorsal and anal fins, and generally carry heavier speckling. Females stay smaller and rounder through the body and often show stronger blue on the gill plate and lower flanks. Sexing juveniles with any confidence is not realistic.
Two fish are sold under the Jack Dempsey name and it is worth being precise, because the price difference is substantial.
| Standard Jack Dempsey (this listing) | Electric Blue Jack Dempsey | |
|---|---|---|
| Species | Cichlasoma octofasciatum / Rocio octofasciata | The same species, a selectively bred colour form |
| Colour | Dark charcoal ground with iridescent blue-green spangles and red fin edging | Pale, largely uniform powder blue to turquoise with little dark ground colour |
| Origin of the strain | Wild-type colour | Captive-bred colour strain, not a wild population |
| Hardiness | Robust and forgiving | Generally slower-growing and more delicate |
| Price | The everyday price you see on this page | Substantially higher — it costs many times more to buy in |
If the blue morph is what you are after, it is a separate listing: see Electric Blue Jack Dempsey. Care requirements are broadly the same; the blue fish is simply less robust and needs a little more attention to water quality and to being out-competed at feeding time.
Plan around a minimum base footprint of 120 x 45 cm for a single adult or a pair — roughly 250 litres in a standard-height aquarium. Floor area matters more than volume here: this is a substrate-oriented fish that patrols and defends ground rather than swimming in open mid-water.
The Jack Dempsey is not a fussy fish about water chemistry, but it is a demanding one about water quality. It eats a lot and produces a lot of waste. Over-filter the tank, change water weekly, and keep nitrate low. That single habit prevents most of the health problems this species runs into.
They are omnivores with a clear preference for aquatic invertebrates, and they will take almost anything offered — which makes overfeeding the easiest mistake to make.
Beef heart and similar mammalian meats are still recommended in older literature. They are poorly suited to a fish's digestion and are associated with fatty degeneration over a long life. Stick to aquatic proteins and a quality prepared food.
Feed once or twice a day, only what is cleared in a couple of minutes, and run a fasting day each week. A well-conditioned Jack Dempsey is muscular and deep-bodied, not swollen.
Juvenile Jack Dempseys are sociable and will share a tank without incident. This is the trap. Aggression arrives with sexual maturity, it is territorial rather than occasional, and it does not fade with age or familiarity. Every stocking decision has to be made for the adult fish.
What can work, in a large enough aquarium:
What does not work: anything small enough to be eaten, anything slow, anything long-finned, and any timid fish regardless of size. A bonded pair is normally settled with each other and hostile to all other conspecifics, so two unpaired mature fish in a standard tank will fight, and one of them will lose badly.
Use the size selector for the live options. The trade-off is straightforward:
Whichever size you choose, the adult aquarium needs to be planned before the fish arrives. Growing a Jack Dempsey on in a small tank and hoping to upgrade later is the most common route to a stunted, badly tempered fish.
They are biparental substrate spawners — both parents guard eggs and fry, and they are good at it.
Given space, filtration and a varied diet, ten years is a realistic lifespan. Most problems are husbandry-driven:
A settled Jack Dempsey is one of the more engaging freshwater fish to live with. They patrol a defined territory, dig, move decor, and watch the room — most keepers find their fish recognises the person who feeds it and comes to the front of the glass. Colour intensifies when the fish is confident, displaying or guarding, and darkens or pales with mood.
They are most active in the middle of the day and around feeding. Expect the aquascape to be rearranged periodically; this is normal behaviour and not a sign of stress. What is not normal is constant hiding or clamped fins, which usually points to water quality, an over-bright bare tank, or a tank mate the fish cannot get away from.
Most people shopping for a Jack Dempsey are really choosing between three or four Central American cichlids of broadly similar size and attitude. The differences that actually matter are adult size, how much aggression you are signing up for, and how big the final tank has to be.
| Fish | Adult size | Aggression | Minimum adult tank | Best for |
|---|---|---|---|---|
| Jack Dempsey | 15-20 cm | High at maturity | 120 x 45 cm, ~250 L | A single striking centrepiece with real personality |
| Convict Cichlid | 10-15 cm | High, but smaller | 90 x 40 cm, ~120 L | The same behaviour in a smaller, cheaper package; breeds relentlessly |
| Firemouth | 13-15 cm | Moderate — mostly bluff | 100 x 40 cm, ~150 L | The gentlest route into Central American cichlids |
| Green Terror | 20-25 cm | Very high | 150 x 50 cm, ~400 L | Experienced keepers with a big tank |
| Red Devil / Midas | 30-35 cm | Extreme | 180 x 60 cm, 600 L+ | Specialists only — see our Red Devil Midas Cichlid |
The Jack Dempsey occupies a useful middle position: big and characterful enough to carry a tank on its own, without needing the 600-litre aquarium a Red Devil or a Managua will eventually demand. That is a large part of why it has stayed popular for the better part of a century.
Jack Dempseys grow quickly given food and space, and the aquarium needs to keep pace. A rough timeline for a well-fed fish:
The commonest way to ruin a Jack Dempsey is to keep it in a small tank "for now". Restricted growth in a young cichlid causes permanent stunting — a fish with a normal-sized body and undersized internal organs — and it shortens life considerably. If the 250-litre aquarium is not going to happen, this is not the right fish.
The Jack Dempsey is not fussy about water chemistry and very fussy about water quality. It eats a lot of protein, produces a lot of waste, and digs the substrate constantly, which keeps detritus in suspension. Filtration should be specified generously.
There is no point fighting the behaviour. A Jack Dempsey will excavate pits, move gravel against the glass and relocate anything it can lift. Design around it:
A tank divided into two or three visual zones is measurably calmer than an open one. A cichlid that can see the whole aquarium treats the whole aquarium as its territory.
Buy one if: you have — or have firmly committed to — an aquarium of at least 120 x 45 cm, you want a single large fish with genuine personality rather than a busy community, you are comfortable with a fish that will not tolerate small tank mates, and you are planning around a decade of fishkeeping.
Look elsewhere if: the tank is under about 200 litres, you want a peaceful community, you have your heart set on keeping several cichlids together in a modest aquarium, or the fish needs to look impressive on the day it arrives.
If the Jack Dempsey is close but slightly too large or too aggressive, a Firemouth or a Convict gives you similar behaviour in a smaller aquarium. If you want to go the other way, the Managua Cichlid and Thick-Lipped Red Devil Cichlid are both bigger, bolder and correspondingly more demanding.
Almost every problem people have with Jack Dempseys is a territory problem, and territory is readable if you know what to look for. Learning the signals lets you intervene before damage happens rather than afterwards.
A comfortable Jack Dempsey holds a moderate, even colour, patrols a defined area of the tank, and comes forward when someone approaches the glass. Fins are held open but not rigid. It will dig, sift substrate and rearrange things — that is contentment, not stress.
A fish defending territory darkens sharply, spreads the gill covers, flares all fins and turns broadside to whatever it is warning off. This is the display posture, and against a tank mate that takes the hint, it ends there. Two fish that both hold the posture will progress to lip-locking and circling, and that is where injuries start.
The most effective single intervention is rearranging the hardscape. Moving rock and wood resets every established territory at once and forces the whole tank to renegotiate, which frequently resolves a standoff that has been running for weeks.
There are two sensible ways to keep this fish, and it is worth deciding which one you are building before you buy.
One Jack Dempsey in a 250-litre aquarium, possibly with a large pleco. This is the easiest option by a wide margin, and it is what most keepers end up doing. The fish gets the entire territory, aggression has no outlet and therefore no target, and the fish becomes noticeably tamer and more interactive with people because it has nothing else to pay attention to. A single, well-coloured adult in a well-scaped tank is a genuinely impressive display.
A Jack Dempsey with other robust cichlids of similar size — Firemouths, Convicts, a Salvini, a Green Terror — needs considerably more space, generally 400 litres and up, and it needs to be planned properly:
The mixed tank is more interesting and much more work. If this is a first large cichlid, the single-specimen route is the one we would recommend.
A Jack Dempsey's dietary needs change as it grows, and a fish fed the same way at 15 cm as at 4 cm ends up either stunted or overweight.
Growing fast and needing protein and frequent meals. Two to three small feeds a day of crushed or small-grade sinking pellets, supplemented with frozen Daphnia, baby brine shrimp and finely chopped bloodworm. At this stage food drives growth, and underfeeding a juvenile costs adult size permanently.
Growth slows and appetite does not. Move to one or two feeds a day of a larger sinking pellet, with frozen foods two or three times a week and a fasting day. This is the stage where overfeeding starts to show as a thickened body profile.
Once daily, or six days a week with one fasting day. A quality cichlid pellet as the staple, plus chopped prawn, mussel and frozen invertebrates a couple of times a week. Vegetable matter — blanched peas, spirulina-based foods — helps digestion in a fish that has stopped growing but not stopped eating.
For a long-lived fish, home-made food gives you full control of the ingredients: white fish, prawn, mussel, a little spinach or pea, blitzed and set with gelatin, then frozen in sheets and broken off as needed. It is cheap, it stores well, and it avoids the fillers in some prepared foods.
This is one of the few large cichlids where UK water chemistry is essentially a non-issue. The recorded range of pH 6.5-8.0 and 90-357 ppm hardness covers virtually every mains supply in the country, from the soft water of the north and west to the very hard supplies across the south and east.
What you should not do is chase a target pH with chemical adjusters. Stability matters far more than the number, and a fish this tolerant gains nothing from adjusted water while losing a great deal to a pH that swings between water changes. Match the aquarium to your tap water and concentrate the effort on filtration and water-change discipline instead.
Few aquarium fish carry as much folklore as this one. Some of it is decades out of date and some of it was never true.
They are Central American, from the Atlantic slope between Veracruz in Mexico and western Honduras. The mislabelling is everywhere in the trade and it matters, because it leads people to pair them with genuinely South American fish that want softer, warmer, more acidic water and a very different temperament of tank mate.
They are aggressive, but they are also among the more manageable large cichlids precisely because they do not get very large. A single adult in a properly sized, well-scaped aquarium is a straightforward fish to keep. The reputation comes almost entirely from people housing several in tanks that are too small.
You can keep a juvenile in one temporarily. An adult needs a 120 x 45 cm footprint. Older books written when the fish was thought to top out around 10 cm are the source of the smaller figures still circulating.
A genuinely outdated recommendation. Mammalian fats are poorly digested by fish and are associated with fatty degeneration of the internal organs over a long life. Aquatic proteins and a quality prepared food do the job better.
It is the same species, Rocio octofasciata, in a selectively bred colour form. It is not a hybrid and not a dyed fish. It is slower-growing and less robust than the standard fish, and much more expensive to buy in, which is why it sits on a separate listing.
Have the aquarium cycled and running before the fish arrives. On arrival, dim the lights, float the bag to equalise temperature, then drip-acclimate. Release into a shaded tank and leave the lights off for the rest of the day.
Expect a new fish to be pale and cautious for several days, and to spend time behind the hardscape. Feed lightly at first and build up over the first week. If the Jack Dempsey is going into an established tank, rearranging the decor on the day it arrives resets existing territories and gives the newcomer a fair chance. Watch the first fortnight closely: this is when stocking mistakes show up, and it is far easier to move a fish then than after a pair has claimed the tank.
24–30°C · pH 6.5–8 · 250L
24–28°C · pH 6–7.5 · 500L
18–26°C · pH 6.5–8 · 30L
23–27°C · pH 7.4–8.4 · 1000L
20–24°C · pH 7–8 · 45L
24–28°C · pH 6.5–7.5 · 2000L
24–28°C · pH 5.5–7 · 60L
18–28°C · pH 6.5–8 · 20L
22–26°C · pH 6–7.5 · 60L
24–28°C
24–28°C · pH 7.5–8.5 · 500L
28–30°C · pH 5.5–7.5 · 300L
22–26°C · pH 6–7.5 · 150L
22–26°C · pH 6–7.5 · 200L
22–28°C · pH 7–8.5 · 10L
23–27°C · pH 5.5–7.5 · 80L
