Threadfin Acara
Acarichthys heckelii
Cichlidae
About
The threadfin acara is a striking, medium-large eartheater relative from the Amazon and Essequibo drainages of South America, named for the trailing filamentous extensions of its dorsal fin. Comparatively peaceful for its size, it spends its day sifting fine sand for food and is best kept in a spacious group where intraspecific squabbles diffuse across several fish.
Care
Provide a large tank of 300 L or more with a deep fine sand bed for sifting, robust filtration and frequent water changes. Keep as a group of five or more and expect vigorous digging.
Diet
Sand-sifting omnivore that filters invertebrates and detritus from the substrate; offer sinking pellets, frozen and live meaty foods plus some vegetable matter.
Tankmate compatibility
Gets along with (15)
Possible with care (205)
Avoid (51)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
What works for this species, most reliable first.
- Extended finsStrong · from about 8 months, and later in a suppressed male
On many cichlids and killifish the male's dorsal and anal fins draw out into trailing points as he matures, while the female's stay rounded.
- VentingA hint only · only on a mature fish, easiest when she is in breeding condition
The method breeders use when the answer has to be right. Hold the fish upside down in a wet hand or soft net and look at the two openings ahead of the anal fin. The forward one is the anus; the one behind it is what you are reading.
- Adult sizeA hint only · only across animals of the same age
In many cichlids, catfish and loaches one sex simply grows larger — usually the male, though there are well-known reversals.
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Frequently asked questions
- What tank size does a Threadfin Acara need?
- A Threadfin Acara needs an aquarium of at least 300 litres (79.3 US gallons) with a footprint at least 150 cm (59.1 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Threadfin Acara need?
- Threadfin Acara does best at 24–30 °C (75.2–86 °F), pH 6–7.8 and a general hardness of 2–15 °dGH.
- What group size does a Threadfin Acara need?
- Threadfin Acara is a social species — keep a group of at least 5 so natural behaviour emerges and stress stays low.
- Is the Threadfin Acara suitable for beginners?
- Threadfin Acara sits in the middle of the difficulty scale — manageable for a careful beginner who has done the reading, but it has specific needs worth researching first.