|A. Heckelii sub-adult. A&G Photo|
A. Heckelii is known by a variety of names, including Heckel's Cichlid and the Threadfin Acara. The adults are very colourful, rather large, and surprisingly laid-back for South American Cichlids - their behavior and size is akin to freshwater angels like P. Scalera or to the various Severums... making them slightly more suitable to community tanks than some other cichlids, though there's still some care to be taken when finding them tankmates.
I have a fondness for these fish, as you can probably tell - they're my first cichlids, and unarguably gorgeous in their full adult colouration and finnage. They're also relatively hardy in my opinion - I'd say this has to do with their origins in the northern part of the Amazon basin, but I could also just be blowing smoke. I'm a fish-keeper, not a formally-trained ichthyologist.
Their natural habitat are slow-moving sections of their rivers as well as flood planes, so they prefer a somewhat lower flow. This is their only complication in handling as they are sensitive to chemical flux, leading to problems like ammonia shock or "hole-in-the-head" disease months or years down the road. This is easily avoided with somewhat-heavier-than-normal water changes or the use of a sump with a highly powerful filter... in practice, this is less of a problem than one would think.
Their natural environment exposes them to 76-84 degrees F, and they respond to the higher end of that range somewhat better, with a pH near 6.2 preferred, and softer water preferred, in the neighbourhood of 10-100 mg/L of General Hardness.
|Same Specimen, 1 Week Younger. A&G Photo|
I've found them to enjoy a varied diet, though they eat food only once it has begun to sink. Blood Worms, Krill-based Predator Sticks, and ordinary Tropical Flake are all devoured readily, and the cichlid will readily hoover up any Algae Disks my tiger hillstream loach ignores. Their diet should include some vegetable matter - blanched spinach and spirulina are the most important sources keepers offer.
Aside from fin nippers and fish that need entirely different conditions, or are overly aggressive, just about any fish over a couple of centimeters makes an okay tank-mate for even an adult specimen, though keep water volumes in mind - the pair of these fish pretty much fill my 55 once they're full grown.
Sexing the fish is difficult, with no external features to rely on to provide a clue. Their spawning behaviour is particularly complex, and it should be noted that attempts to reproduce it in home aquaria usually fail. Having said that, even the impossible often happens by accident, and I'm told the fry themselves are easy to raise.