Jack Dempsey Cichlid (Cichlasoma octofasciatum bioce) - Cichlid Fish for Sale UK

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.

Where Does the Jack Dempsey Come From? Natural Habitat Explained

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.

What Does a Jack Dempsey Look Like? Colour, Size and Sexing

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.

Standard Jack Dempsey or Electric Blue? Which One This Is

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.

How to Set Up the Right Tank for a Jack Dempsey

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.

• Substrate: sand or fine, rounded gravel. They dig, and sharp gravel damages mouths.
• Hardscape: solid rockwork and bogwood, seated on the base glass rather than on the substrate so digging cannot undermine it.
• Sightlines: break the tank up. A fish that cannot see the whole aquarium at once is a less stressed and less aggressive fish.
• Plants: expect them to be moved. Anchored species such as Anubias and Java fern tied to wood survive; anything rooted in the substrate usually does not.
• Filtration: generous and mechanically strong. This is a messy, heavy-feeding fish.
• Lid: secure. Large cichlids jump, particularly when startled or squabbling.

Jack Dempsey Water Parameters: Temperature, pH and Hardness

• Temperature: 20-30°C. A steady 24-26°C suits them well; the upper end speeds growth but shortens lifespan.
• pH: 6.5-8.0. Genuinely wide — no need to adjust for most UK water.
• Hardness: 90-357 ppm, roughly 5-20 dGH. Hard, alkaline tap water is fine.

What Do Jack Dempseys Eat? Complete Feeding Guide

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.

• Staple: a good quality sinking cichlid pellet sized to the fish.
• Rotate: frozen Daphnia, mosquito larvae, bloodworm, and chopped prawn or shrimp.
• Useful extra: home-made gelatin-bound mixes let you control the ingredients for a large, long-lived fish.

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.

Jack Dempsey Aggression and Tank Mates: An Honest Guide

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:

• Other robust Central American cichlids of comparable size — see Red Devil Midas Cichlid, Managua Cichlid and Thick-Lipped Red Devil Cichlid
• Large armoured catfish such as common and sailfin plecos
• Fast, deep-bodied characins such as Blackberry Silver Dollar

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.

Which Size Should You Buy?

Use the size selector for the live options. The trade-off is straightforward:

• Small (3-4 cm): the best value and the easiest to settle in. Plain-coloured on arrival, and you get to grow the fish on and watch the colour develop.
• Medium (5-6 cm): hardier in transit, colour starting to show, still a long way from adult size.
• Large and XL: closer to the finished article and a much shorter wait for full colour, at a higher price. These need the full-size aquarium ready on day one.

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.

How Do You Breed Jack Dempsey Cichlids?

They are biparental substrate spawners — both parents guard eggs and fry, and they are good at it.

1. Grow on a group of six or more young fish and let a pair form naturally. Forced pairings frequently end in a dead fish.
2. Provide flat rocks or slate as spawning sites, and a divided tank layout so a rejected fish has somewhere to go.
3. Condition the pair on frozen and live foods, and raise the temperature towards the upper end of the range.
4. The female lays on a cleaned flat surface; both parents fan and defend the eggs.
5. Eggs hatch in a few days; the parents move the wrigglers to pits dug in the substrate.
6. Feed free-swimming fry on baby brine shrimp and finely crushed prepared foods.
7. Expect the pair to become extremely aggressive while guarding. Remove other tank mates or accept losses.

Jack Dempsey Health, Lifespan and Common Problems

Given space, filtration and a varied diet, ten years is a realistic lifespan. Most problems are husbandry-driven:

• Hole-in-the-head / HLLE — associated with poor water quality, high nitrate and a monotonous diet. Prevention is water changes and food variety.
• Fin and mouth damage — almost always fighting. Reassess stocking rather than treating repeatedly.
• Bloating and obesity — overfeeding, especially on rich foods with no fasting days.
• Stunting — a fish grown on too long in a small tank. Irreversible, and it shortens life.
• Jumping — keep the aquarium covered.
• Whitespot after a move — usually a temperature swing. Treat the tank and correct the cause.

Day to Day Behaviour: What to Expect

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.

Why Buy Your Jack Dempsey From Tropical Fish Co

• Named to the supplier's own record, so the fish you receive is the fish on the page — the standard Jack Dempsey, not the blue morph.
• A real size ladder, so you can buy a juvenile to grow on or a larger fish that is already colouring up.
• Packed for the journey and shipped with a licensed live-animal courier.
• Live Arrival Guarantee on every livestock order.
• Care information written to be used, including the parts about adult size and temperament that are easier to leave out.

Jack Dempsey vs Other Central American Cichlids

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.

Growth Timeline: From 4 cm to Adult

Jack Dempseys grow quickly given food and space, and the aquarium needs to keep pace. A rough timeline for a well-fed fish:

• On arrival (3-4 cm): plain grey-brown with faint vertical barring and a scatter of pale spots. Almost no blue.
• 3-6 months (6-9 cm): body deepens, the first iridescent spangles appear along the flanks, barring becomes more defined.
• 6-12 months (10-14 cm): the real colour arrives. Ground colour darkens, spangling spreads across the body and into the fins, red fin edging develops. Sexual maturity, and with it territorial behaviour, typically begins in this window.
• 12-24 months (15-20 cm): approaching adult size. Males outgrow females and develop longer, more pointed fins.
• Beyond 2 years: growth slows sharply; colour continues to improve for several more years.

Filtration, Maintenance and Water Changes

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.

• Filtration: an external canister rated well above the tank volume, or two filters, so maintenance on one never leaves the tank unfiltered. Mechanical capacity matters as much as biological here.
• Flow: moderate. They come from slow water, so aim the outlet along the back glass rather than across the open floor.
• Water changes: 30-40% weekly on a stocked adult tank. This single habit prevents most of the health problems associated with the species.
• Nitrate: keep it low. Chronic high nitrate is strongly associated with head and lateral line erosion in large cichlids.
• Heater: use a guard or an external inline heater. A digging adult will dislodge or break an unprotected glass heater eventually.
• Substrate: siphon the open areas weekly; the fish will have redistributed most of it since the last clean.

Aquascaping for a Fish That Digs

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:

• Seat all rockwork on the base glass, before the substrate goes in. Rock stacked on top of sand will be undermined and can fall.
• Use bogwood as the main structure — it is lighter, harder to topple, and provides the sightline breaks that reduce aggression.
• Attach plants rather than planting them. Anubias and Java fern tied to wood survive indefinitely. Rooted stem plants do not.
• Leave a defined open area at the front. That is where the fish will patrol and where you will actually see it.
• Round substrate only. Sand or smooth fine gravel; sharp grades damage mouths on a fish that sifts.

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.

Common Mistakes With Jack Dempseys

Is a Jack Dempsey Right for You?

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.

Understanding Territory and Body Language

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.

What a settled fish looks like

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.

Display and threat

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.

Warning signs to act on

• One fish permanently in a corner or at the surface — it has lost and has nowhere to go. Move it or add cover immediately.
• Torn fins or a damaged mouth — restructure the tank or reduce the stocking; treating the injury without fixing the cause achieves nothing.
• A fish that stops eating — in a mixed tank this is usually being kept from the food, not illness.
• Persistent dark stress barring with clamped fins — different from display darkening; the fish is not confident anywhere in the tank.

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.

Species Tank or Mixed Central American Tank?

There are two sensible ways to keep this fish, and it is worth deciding which one you are building before you buy.

The single-specimen tank

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.

The mixed Central American tank

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:

• Introduce everything at once, or at least add the Jack Dempsey last so it cannot establish first.
• Break the floor into zones with substantial hardscape so no fish can see the whole tank.
• Over-stock slightly rather than under-stock. With cichlids, aggression spread across several targets is less damaging than aggression focused on one.
• Keep a spare tank running. Sooner or later one fish will need removing, usually at short notice.
• Match sizes. A noticeably smaller cichlid becomes a target rather than a rival.

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.

Feeding Through the Life Stages

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.

Juveniles, 3-8 cm

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.

Sub-adults, 8-15 cm

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.

Adults, 15 cm and up

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.

Water Chemistry: Working With UK Tap Water

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.

• Hard, alkaline water (most of southern and eastern England): ideal as it comes. No adjustment needed.
• Soft, acidic water (parts of Scotland, Wales, the south-west): also fine, though very soft supplies can be prone to pH instability. A little crushed coral in the filter adds buffering if pH is drifting between water changes.
• Chloramine-treated supplies: use a dechlorinator rated for chloramine, not just chlorine.

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.

Jack Dempsey Myths Worth Correcting

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.

"Jack Dempseys are South American cichlids"

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 too aggressive to keep"

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 one in a 100-litre tank"

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.

"Feed them beef heart for growth"

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.

"The Electric Blue is a different species"

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.

Acclimation and the First Two Weeks

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.