Care
Cardinal tetras resemble their cousin the Neon tetra (P. innesi) but their German common name of Red Neon describes the main difference rather well - this fish displays a red belly lacking in its more mainstream relative. In the wild, these fishes inhabit clear water streams and creeks protected from extremes of temperature by the forest shade. Seasonal rains make for distinct changes in the habitat and the wet season allows adult fish to spawn amongst the marginal vegetation after sheltering among the leaf litter above the stream bed.
Cardinals are at their best in soft water, where they'll live longer, grow larger and show better colour. As with many small tetras, an almost annual life cycle is replaced with a longevity that can be measured in years in captivity. They're sociable fish but observations in the wild reveal that they often forage in modest numbers (5-15 individuals) before coming together to form larger shoals. There's no denying that fifty or more fish makes for a very impressive spectacle in the aquarium but groups of six or twelve will be content in most suitable aquaria. Natural habitats seem to feature leaf litter or aquatic plant cover and these are welcome components of a suitable home set up. These conditions are often found in planted aquaria filled with RO water and running CO2 supplementation.
Most cardinals seen in shops are captive bred but an important sustainable export trade revolves around this species in its rainforest home. As the continued existence of these tetras is dependent on preservation of their habitat, the value of exports protects the fishery from destructive exploitation. For this reason, buying wild-collected fish should be considered as a positive conservation option - just remember that these Amazonian natives will be used to excellent water quality and low nitrates.
In addition to the unbeatable wild type, an albino form is seen which may be labelled as Gold. Lighting will accentuate different colours in these fish, red is more striking in brightly lit conditions
Feeding
Offer a varied diet including a good quality flake, micropellets, and small frozen foods such as mosquito larvae and daphnia.
Breeding
The water must be extremely soft and acidic, and because Cardinal Tetras are thought to lay their eggs in darkness, the spawning aquarium must be darkened. It is a good idea to place a grid or a layer of sterilised marbles on the bottom of the spawning tank in order to protect the eggs from the parents. The temperature should be set at the higher end of their range. Female Cardinal Tetras can lay upwards of 150 eggs, some report over 300. Once the eggs have been laid/fertilised, the pair should be acclimatised back to the main aquarium. As the eggs are photo-sensitive, they should remain in darkness, and should hatch within 36 hours. Once the fry have absorbed their yolk sacs and become free-swimming, much difficulty in feeding them ensues, this being due to their diminutive size. Infusoria and liquid fry foods should be offered, moving on to newly hatched brineshrimp after a week or so. Remember that the fry are also light-sensitive and should remain under very subdued lighting (and stable water conditions) for some time.
