Classic Car Intelligence
  • Species: Electric Blue Jack Dempsey

  • Species: Jack Dempsey

The Mysterious Electric Blue Jack Dempsey

07 August 2010

The fish we call the Electric Blue Jack Dempsey (often shortened to EBJD) has been around since at least the mid 1980s, though it has only very recently appeared in the tropical fish trade. Compared to the standard Jack Dempsey, the Electric Blue Jack Dempsey is a vivid turquoise blue in colour. It also tends to be smaller than normal Jack Dempseys as well as somewhat less aggressive. This combination of traits has ensured that among some hobbyists at least Electric Blue Jack Dempseys have become popular and highly sought-after fish.

However, there are some odd things about this cichlid. It is physically weaker than the normal Jack Dempsey, and requires more carefully controlled environmental conditions to do well. They tend to be more prone to diseases than regular Jack Dempseys too. In itself this isn’t altogether surprising; inbred ‘fancy’ forms of fish are almost always less robust than the more genetically varied forms they were bred from. You can see the same thing with angelfish, guppies, and goldfish. But what is more unusual is the near-zero fertility of the Electric Blue Jack Dempsey. When two Electric Blue Jack Dempseys are mated their eggs almost never hatch, and even the few fry that do emerge only live for a few days at most.


While it is often rumoured that the Electric Blue Jack Dempsey is a hybrid of some sort, in much the same way as the Blood Parrot Cichlid or the Flowerhorn Cichlid, this does not appear to be the case. Or at least, if there are genes from other cichlid species within the genetic make-up of the Electric Blue Jack Dempsey, they only make up a tiny percentage of the total genome. It’s worth mentioning that many of the cichlids traded by hobbyists are hybrids to some slight degree, particularly now that fish that were once thought to be a single species are now recognised to be complexes of many different species. That’s the case with severums for example, so even a captive-bred severum assumed to be a pure species very likely has some other Heros species in its ancestry beyond the standard Heros severus.

In fact it is much more likely that the Electric Blue Jack Dempsey is precisely what its advocates maintain it to be: a mutant form of the Jack Dempsey cichlid, Rocio octofasciata. According to an article in the American fishkeeping magazine ‘Tropical Fish Hobbyist’, the Electric Blue Jack Dempsey first appeared when the Argentinian aquarist Hector Luzardo mated a pair of apparently normal Jack Dempseys. A proportion of the fry were paler and weaker than the others. These fry looked and behaved differently, and were picked on by the other fry in the tank. Luzardo isolated these fry, and as they developed he found that their pale colouration gave way to brilliant blue. Besides their different colours and markings, these new fish grew more slowly and exhibited somewhat less aggression.

Because Electric Blue Jack Dempseys are difficult to breed at home, the species spread through the hobby only very slowly. Even now they are comparatively pricey fish, up to ten times the price of regular Jack Dempseys. While the idea that they’re hybrids has been largely debunked, the Electric Blue Jack Dempsey retains a somewhat dubious status within the cichlid-keeping hobby. Some aquarists like the fish, while others don’t. Ultimately this comes down to personal taste rather than ethics; as an aquarium fish, it’s at least as viable as the standard Jack Dempsey and not notably crippled as is certainly the case with the Blood Parrot.


Although the Electric Blue Jack Dempsey is probably a mutant form of the standard Jack Dempsey, its genetics are peculiar. When two Electric Blue Jack Dempseys are mated they produce non-viable eggs. If any fry to hatch, they usually die within a couple of days. Luzardo discovered that the adult Electric Blue Jack Dempseys couldn’t be mated, and to create more of these fish he had to perform further crosses between Electric Blue Jack Dempseys and normal Jack Dempseys.

In terms of genetics, the electric blue gene (often referred to as “b”) is recessive compared to the normal gene (“B”). As with any other trait, the fish has two genes for this feature in its chromosome. Normal Jack Dempseys are “BB”, Jack Dempseys carrying the electric blue trait but not exhibiting it would be “Bb”, and Electric Blue Jack Dempseys would be “bb”. For whatever reason, the “bb” situation renders the fish unable to produce viable fry, which is why successful production of Electric Blue Jack Dempseys relies upon cross carriers (“Bb”) with Electric Blues (“bb”). Roughly half of their offspring will be carriers, and the other half Electric Blue Jack Dempseys.


The production of Electric Blue Jack Dempseys requires two successive matings. Firstly there’s a mating between a male Electric Blue Jack Dempsey (“bb”) and a female normal Jack Dempsey (“BB”). The resulting fry will all be carriers, “Bb”, i.e., they’ll be carrying the electric blue gene but not exhibiting it. They will look like normal Jack Dempseys. A female carrier will then be crossed with another Electric Blue Jack Dempsey to produce a second generation of fry. She won’t be crossed with her father because of the risk of inbreeding, so at least two male Electric Blue Jack Dempseys are essential for good quality offspring. If all goes well, half of the resulting fry will be carriers and half of which will be Electric Blue Jack Dempseys.

Breeding Electric Blue Jack Dempseys is a challenging as breeding the regular sort. Sexing these fish is very difficult, and though males may have slightly longer dorsal and anal fins, the only 100% reliable approach is to examine the genital papillae on sexually mature fish. As with most other cichlids, this is narrow and pointed on males, and broad and rounded on females. Males are extremely aggressive, and are best introduced to females with a tank divider such as egg crate in place. Alternatively, a large aquarium could be used with one male and several females, the aim being to allow the male to pair off with the female he chooses. Other details of breeding Electric Blue Jack Dempseys, such as spawning sites and suitable foods for fry, are similar to those relevant to breeding regular Jack Dempseys.


As noted earlier the Electric Blue Jack Dempsey tends to be a bit less hardy than the standard sort, especially when young. So while water chemistry, water quality and temperature need to be the same as those for standard Jack Dempseys, more care should be taken to ensure good, steady conditions. Zero ammonia and nitrite are essential, and nitrate should be as low as practical, ideally below 20 mg/l. Water chemistry should be moderately hard to hard, neutral to slightly basic; 10-20 degrees dH, pH 7-8. Aim for a middling water temperature around 22-24 degrees C, slightly higher for breeding.

Like most Central American cichlids these fish like to dig, but sturdy plants such as giant Vallisneria, Amazon swords, Java ferns and Anubias are usually left alone. Otherwise use rocks and bogwood to decorate the tank. Floating plants will provide useful shade that encourages these fish to act less nervously.

Diet is unproblematic because this species readily takes all types of dried and frozen foods. Wild fish are opportunistic predators, but some plant-based foods, such as cooked peas and spinach, should be offered periodically. As with all cichlids a combination of poor diet and high nitrate levels will make Electric Blue Jack Dempseys more vulnerable to Hexamita infections and Hole-in-the-Head Disease.

Social behaviour

While sometimes described as less aggressive compared to the regular Jack Dempsey, it would be inaccurate to describe the Electric Blue Jack Dempsey as a peaceful fish. This is not a community fish by any standard! Tankmates need to be of appropriate size and able to either very retiring, fast enough to swim away from trouble, or otherwise able to return any aggression visited upon them. Ideally, Electric Blue Jack Dempseys are kept alone or as mated pairs, but potential tankmates include Mexican tetras, medium to large-sized plecostomus-type catfish, and other moderately aggressive Central American cichlids such as Convict Cichlids and Texas Cichlids.