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Threadfin Acara – Acarichthys heckelii

Threadfin Acara - Acarichthys heckelii

Cichlids are a very ancient and extensive classification of fishes dating back millions of years before, for example, dinosaurs. Cichlids probably originated around 550 million years ago (give or take a month or two 😀) and there are somewhere in the region of 2,000 to 3,000 different species, of which around 1,700 have been classified (at the time of writing).

Cichlids can make excellent community fish but you should take care because not all Cichlids are good community fish and may devastate an established aquarium, treating their tank mates as food, so before choosing a Cichlid, please ensure that you know whether or not your choice will be appropriate to your needs.

Is Threadfin Acara (Acarichthys heckelii) a good community fish? Threadfin Acara (Acarichthys heckelii) should be considered to be an excellent community fish assuming that the community is one of non-aggressive, non-predatory species. Threadfin Acara (Acarichthys heckelii) is suitable for all community aquariums that are of appropriate size although it can be somewhat aggressive during breeding. 

Key Facts about Threadfin Acara (Acarichthys heckelii)

CategoryKey Facts
Common name(s)Threadfin Acara Cichlid
Scientific nameAcarichthys heckelii
Originate fromAmazon river basin in Brazil, Colombia, Guyana, and Peru in South America
Care requiredEasy to care for and very beautiful
TemperamentRelatively placid community fish
Colour & FormOval-shaped body with very elegant finnage
LifespanUp to 8 years
Adult sizeUp to 10 inches – Female Fuller-bodied than male
DietOmnivorous – eats Daphnia, Bloodworm, Tubifex worms and pellet food in the aquarium.
Aquarium size48 inches in length or greater
Compatible withMost other Tetras, Barbs, Danios, Guppies and other livebearers, dwarf cichlids, smaller Gouramis, catfish and loaches that live in fairly neutral, soft water
Avoid keeping withLarge and/or aggressive species and fin-nippers in too small an aquarium
BreedingEasy if you put the fish in the right environment.
Water temp75 – 84 Fahrenheit
Water pH6.0 to 7.2
Water hardness (dGH or dH)4 to 15 dGH

Origins of Threadfin Acara (Acarichthys heckelii)

Threadfin Acara (Acarichthys heckelii) is found in the Amazon river basin in Brazil, Colombia, Guyana, and Peru in South America. 

It is usually found in nature in soft, slightly acidic, flowing water. 

Basic Characteristics of Threadfin Acara (Acarichthys heckelii)

Threadfin Acara (Acarichthys heckelii) will grow to almost 10 inches in length in the aquarium The mature female will tend to be fuller-bodied than her male counterpart. In young fish, it is difficult (pretty impossible) to distinguish between the sexes so if you are purchasing young fish then buy half-a-dozen or more and you should have a mix of the sexes but please bear in mind that a group of what will become quite large fishes will require adequate space in which to live. When you find that two of the group have paired off then the remaining fish should be moved to a different tank, as the male can be particularly territorial whilst breeding.

The lifespan of Threadfin Acara (Acarichthys heckelii) is around eight years but this can vary enormously depending on tank conditions and general health.

Threadfin Acara (Acarichthys heckelii) prefers neutral to slightly hard, alkaline water, with a pH of 6.0 to 7.2 in and a temperature range between 75 and 84 degrees Fahrenheit and 4 to 15 dGH. Threadfin Acara (Acarichthys heckelii) will be comfortable with other species of similar size that prefer this type of water chemistry.

Threadfin Acara (Acarichthys heckelii), being a Cichlid, is a very gentle species but will become very territorial whilst mating and the male, in particular, will chase other fish to the other end of its territory, should they come close. Because territorial behavior varies widely amongst individual fish, you may find that yours may chase other fish away whilst another may launch a full-on attack so you need to be particularly vigilant at spawning times.

Threadfin Acara (Acarichthys heckelii), whilst being a relatively large fish has a relatively small mouth so it is usually quite safe to keep it in company with much smaller species, though, due to its size, a larger aquarium is strongly advised.

The Threadfin Acara (Acarichthys heckelii) gets on well with pretty well all other fishes (that are not reputed to be predatory or fin-nippers) and is generally an excellent community species.

Threadfin Acara (Acarichthys heckelii) will generally dwell near the middle of the water column and will enjoy a fine substrate, and plenty of rocks, as the female will spawn either on the substrate or on rocks within caves which the she will prepare for the purpose.

The physical appearance of Threadfin Acara (Acarichthys heckelii)

  • There is very little if anything to distinguish the male from the female. The body of the Threadfin Acara (Acarichthys heckelii)  is a beautiful, oval shape from its almost centrally located mouth to the ends of the base of the dorsal and anal fins, where the caudal peduncle begins.
  • The head of the Threadfin Acara (Acarichthys heckelii), as far back as the eye is grey in the adult fish and the eye tends to have an orange/red color to the upper, front of the iris. On the gill plates and under the eyes, there is some gold coloration with speckles of iridescent, metallic gold.
  • Behind the gill plates of the Threadfin Acara (Acarichthys heckelii), the body is a light silverish grey but is distinctive in that it has around ten rows of the iridescent, metallic gold scales, evenly spaced and running horizontally to the end of the caudal peduncle (and continuing along the rays of the caudal fin, almost to its tip). In the middle of the body of the Threadfin Acara (Acarichthys heckelii), there is a pinkish-orange spot, which is more-or-less circular, around one inch in diameter and almost looks as if it has been painted on.
  • The dorsal fin is long and extended at the rear. The spiny rays are a milky white and the spaces between are clear (hyaline). There is a hint of a russet color at the root of the fin. About one-third of the way along the dorsal fin the iridescent, metallic gold speckles return in increasing numbers, along the rays of the fin and between these there is a red-brown tinge to the rays. The rear rays of the dorsal fin have red-brown “threads” extending backward for around three to four inches.
  • The pectoral fins are unremarkable, being that they are clear (hyaline).
  • The ventral fins have a red-brown leading edge and, like the dorsal din, several of the outermost rays extend backward, beyond the fin as a whole, for as much as one inch.
  • The anal fin of the Threadfin Acara (Acarichthys heckelii) is reddish-brown in color and extends to a point at the rear. It also has the iridescent, metallic gold speckles, but fewer in number, along the root and inner trailing edge of the fin.
  • The caudal fin has already been described but it is noteworthy that the upper and lower rays also extend backward, well beyond the main fin as red-brown threads.
  • In respect of Threadfin Acara (Acarichthys heckelii), it is probably wise to avoid including known fin-nippers.

The living environment for Threadfin Acara (Acarichthys heckelii)

Threadfin Acara (Acarichthys heckelii) enjoys being in and around rocks and caves. Only one adult pair from a single generation should be kept in the aquarium unless the aquarium is of sufficient size to facilitate two (or more) territories.

Threadfin Acara (Acarichthys heckelii) will appreciate a soft substrate, as they love to rummage around for food.

Note that Threadfin Acara (Acarichthys heckelii) is biparental will generally make good parents for any brood that they are rearing. They are not, however, monogamous for life. It is also reported that a breeding pair may fight with each other and this can have fatal consequences for one or both of the pair but this is not something that I have witnessed.

It is recommended that Threadfin Acara (Acarichthys heckelii) are kept as a small shoal only until two of the adults have paired up, after which, the remainder of the shoal should be relocated to a different aquarium. The male, in particular, can be very territorial (but does not appear to launch a physical attack, merely chasing away “trespassers”) but setting up the tank so that sightlines are broken up will mitigate the risks of territorial behavior in general. 

When purchasing Threadfin Acara (Acarichthys heckelii) it is generally recommended to buy around six fish. It will be impossible to sex the fish when purchasing them as immature specimens but, in due course, they will find their own mate and are, from that point, generally both biparental. Remember that this fish will grow to up to ten inches in length so be certain that you have sufficient space in which to house them properly.

Overall, Threadfin Acara (Acarichthys heckelii) are the most attractive, unusual and elegant addition to your aquarium.

The diet of Threadfin Acara (Acarichthys heckelii)

Threadfin Acara (Acarichthys heckelii) is primarily omnivorous. It loves live food, feeding on a range of invertebrates in nature. In the aquarium a diet of live or frozen Artemia, Bloodworm and Daphnia is recommended and Threadfin Acara (Acarichthys heckelii) will readily eat pelleted food and flake food. That said, they prefer to stay close to the bottom of the water column and browse the rocks and plants. For this reason, a fine substrate is recommended.

Sexual differences in Threadfin Acara (Acarichthys heckelii)

It is very difficult to distinguish the sex of the Threadfin Acara (Acarichthys heckelii) until it becomes adult. The adult female develops a fuller body than the male. The female is also fuller-bodied when viewed from above when carrying eggs (gravid).

Aquarium size for Threadfin Acara (Acarichthys heckelii) 

It is generally advised that the minimum tank size for Threadfin Acara (Acarichthys heckelii) should be one of at least 48 inches in length or more due to the fact that a shoal of around six per species should be maintained initially and the adult fish are territorial within their own species and within their own genus. This will enable your Threadfin Acara (Acarichthys heckelii) to find an area of the aquarium which the pair can call home. A smaller tank will be too restrictive (unless it is a breeding tank) and the fish will suffer as a result whilst a larger tank is always to be recommended.

In a community tank, including some floating Java Moss will give smaller fish and any fry a safe haven from larger or more vigorous species and it certainly helps to break up the sightlines in the aquarium. Plenty of rocks are advised for Threadfin Acara (Acarichthys heckelii) because they have evolved to gather around and amongst them.

There is a predominance of so-called “Nano tanks” available but, being old-fashioned, I prefer my fishes to live in an environment which, at least, attempts to mimic nature, rather than living in what I would liken to a piscine prison cell. The tank should be well-planted but with clear areas where the fish can swim freely. The water should have a certain amount of movement, as Threadfin Acara (Acarichthys heckelii) enjoy a flow of water.

Threadfin Acara (Acarichthys heckelii) – Videos

Young Threadfin Acara (Acarichthys heckelii) video care guide

Threadfin Acara (Acarichthys heckelii) video – breeding pair

Are you keeping tropical fish as a hobbyist or as a breeder?

This is a question too often ignored in my humble opinion. If you are a breeder (either commercially or as a hobbyist who gives away young fish to other hobbyists) then you will need the resources to move fish into breeding tanks in order to maximize the yield of fry that will grow up either for sale or to give them away.

If you are keeping fish for the joy of observing them in something resembling a natural habitat then you may feel that it is appropriate to allow nature to take its course and, as and when different species breed, then many of the eggs (and surviving fry) will be eaten either by their parents or by other fish in your aquarium. This is the natural order of things because this is what will happen in nature. The fittest may well survive to reach adulthood.

Ultimately, the choice is yours to make.

How do Threadfin Acara (Acarichthys heckelii) breed?

In total, the female Threadfin Acara (Acarichthys heckelii) could lay up to 2000 eggs during a single spawning. Threadfin Acara (Acarichthys heckelii) will lay the eggs either on a cleaned rock in a cave in the wild so a large, upturned terracotta pot with a suitably-sized entrance is generally recommended in the aquarium. The female will prepare the breeding area and then seek to attract a suitable male with which to pair.

Whilst the male will pair with a female for breeding and rearing the fry until they are around half-an-inch in length, he will have a “harem” of females with which he will mate at different times.

Threadfin Acara (Acarichthys heckelii) becomes sexually mature after two to three years so, if you want to breed them then be prepared to be a little patient.

The female will constantly fan the eggs to ensure that they are getting sufficient oxygen and she will eat any unfertilized eggs. In the meantime, the male will chase away any and all threats to his territory.

Threadfin Acara (Acarichthys heckelii) eggs will hatch in around three days, depending on water temperature and chemistry. The fry will become free-swimming around three days later and the parents will take care of them until they are around half-an-inch in length. Generally, the fry will stay close to the breeding cave until they are large enough to fend for themselves.

It is generally true that Threadfin Acara (Acarichthys heckelii) make really good parents and will not prey on their own young. In general, the male will protect the territory whilst the female will tend to care for the eggs and fry but these roles are interchangeable.

The male will provide “overwatch” around the broader area, gently warding off potential predators.

The Threadfin Acara (Acarichthys heckelii) takes responsibility for post-spawning care and may become aggressive if it feels that the brood is threatened. For this reason, if possible, a breeding tank is recommended.

If Threadfin Acara (Acarichthys heckelii) feels threatened, it will defend its brood.

In a well-planted aquarium with floating Java Moss, the Cichlid will often spawn in the community tank and at least some of the fittest fry will survive to adulthood by hiding in the Java Moss or, with Threadfin Acara (Acarichthys heckelii), in the caves of the rocks.

In a breeding tank, it is always a good idea to include a few aquatic shrimp, as they will consume any unfertilized or dead eggs but won’t tend to predate on viable eggs.

Breeding tank for Threadfin Acara (Acarichthys heckelii)

You should prepare a tank of around thirty gallons in size with mature, soft, acidic, flowing water. The water should have a low level of light and broad-leaved plants together with lots of clusters of rocks on which the female will lay her adhesive eggs. 

It is recommended that the substrate consists of a fine substrate (sand) without sharp edges. 

Arrange your tank heating so that you can slowly remove up to half of the tank water and then replace it with collected rainwater (very slightly cooler than the aquarium water – but not so much that White Spot could result) and repeat this daily until the Cichlids spawn. This water and temperature change may encourage spawning, as it mimics nature. The rainwater is most important though some argue that tap water is fine.

Cichlids prefer to spawn where the water is flowing so a decent pump is required to synthesize that flow.

Feed up your Cichlids on bloodworm, which will sink to the bottom and burrow into the substrate. Your Cichlid will love rooting out the bloodworm and it can help to trigger spawning.

You may also wish to introduce baby brine shrimp, mosquito larvae or tubifex worms as an inducement to reproduction and live food will be very much appreciated. This will also tend to divert the attention of the Threadfin Acara (Acarichthys heckelii) from preying on their own eggs and fry though cannibalism is not characteristic of Threadfin Acara (Acarichthys heckelii).

Reduce the water movement by turning down the pump once the eggs are laid – only regular aeration is now required. Keep the lights off (or very low) and the tank dark (or fairly dark)  because eggs and fry can be particularly sensitive to the light.

The eggs will hatch typically in three days depending on tank temperature and conditions and the fry will become free-swimming after around three days more. 

Keep the tank more-or-less unlit for the first week or so then gradually increase the lighting. Bear in mind that the eggs and fry of a fish as small as the Cichlid will be tiny indeed so you may need to use a magnifier “app” on your smartphone or a macro lens to see anything at all. A collection of eggs is generally easy to spot, as they look like a collection of tiny, pearls.

The newly hatched fry will feed firstly on their yolk sac and remain fairly static but, once free-swimming, can be fed infusoria and will also thrive on egg yolk during the first two to four weeks. 

Once the fry are free-swimming and their yolk sacs are depleted, then add baby brine shrimp and/or white worms. Once the fry are sufficient in size not to be treated as a snack then they can be introduced into the community tank where they will join the existing shoal. Before moving the adolescent fish into the community tank ensure that you have balanced the water temperatures to mitigate the risk of White Spot or other diseases being triggered.

Unless you are breeding commercially, you may wish to consider moving the fry into the community tank sooner rather than later. It may seem harsh but the adult fish in the tank will deal with any fry that are unlikely to survive to adulthood in the wild and you are synthesizing, to the best of your ability, a wild environment. The fittest fry will probably survive whilst the rest will be dealt with by the community.

Should your Threadfin Acara (Acarichthys heckelii) have a special diet for breeding?

Adult Cichlids don’t need any particular inducement to breed. That said, it has been suggested that adding tubifex, bloodworm or mosquito larva may encourage them, presumably because the addition of a new food may “fool” the fish into thinking that it is breeding time. From my own experience, I would always recommend keeping all of your fish in the best possible condition at all times, as this is good for the wellbeing of your fish.

Featured image courtesy of Creative Commons.

Mike Wheeler

I started keeping freshwater tropical fish in 1972 and it has been something of a passion ever since. In this website, my aim is to build up an everyman's guide to help the everyday aquarist get the best from this inspiring and entertaining hobby.

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