Care
Within the vast order Characiformes (Characins), sits the Family Crenuchidae (South American Darters). Crenuchidae is further split into two sub-families, Crenuchinae and Characidiinae, together comprising 93 species across 12 genera, with many more species currently undescribed. The genus Characidium (sub-family Characidiinae) is the most speciose, with some 64 species, mostly from coastal South America. These fishes are small, usually around 7.5cm (3"), and live on the bottom in fast-flowing, highly-oxygenated freshwaters, often in the vicinity of rapids and waterfalls. The elongate body shape and position of the fins are an adaptation for living in torrential waters and allow them to forage about on the substrate whilst maintaining position in the current. Darter Tetras are notoriously hard to identify to species level and most imports are labelled incorrectly. However, they do all share similar specialist care requirements, which we will detail here. A requisite for their long-term wellbeing is highly oxygenated, relatively cool water with plenty of current. Provide a sandy substrate along with plenty of nooks and crannies formed from pebbles, smooth rocks, pieces of slate, and tangles of driftwood - ensuring that there are a few visual barriers and some calmer resting areas out of the main flow. Although plants are not found in any great abundance in the fast-flowing waters of the natural habitat (so are not considered essential), robust species such as Anubias and Microsorum tied onto driftwood will help with water quality and will make the aquarium look more aesthetically pleasing, as well as creating more hiding places. Like other species that inhabit fresh running waters, these tetras will not tolerate a build-up of nitrates within the aquarium and require excellent water conditions at all times if they are to thrive - so powerful filtration and regular partial water changes are crucial. Additional water movement could be provided by extra powerheads, and a decent sized air pump is always a handy backup in warmer weather. The best way to keep these gregarious fish is in dense groups of at least 12, and many more where space allows. They may have minor squabbles amongst themselves from time to time, but no real harm should ensue, particularly if there are lots of hiding places available. Larger groups will certainly help to reduce any arguments, as then no single fish will bear the brunt of any antagonistic behaviour, with it instead being spread throughout the shoal. Darter Tetras are perfectly peaceful towards other fish, and good companions could include species which enjoy similar environmental conditions, such as some of the smaller Barbs, brook loaches, Crossocheilus, Danios, Devarios, Garras, hillstream loaches, other small, temperate characins, and small subtropical loricariids (suckermouth catfish). Ensure that the aquarium has tight fitting coverslides with no gaps where equipment feeds into the tank, as these fish are expert jumpers, and many species can actively climb up the glass with ease. May also be seen on sale as Darter Characin.
Feeding
In the wild, these fish feed predominantly on tiny insects and their larvae, so will require regular feedings of bloodworm, white mosquito larvae, black mosquito larvae, vitamin-enriched brineshrimp, daphnia, cyclops etc. Some may eventually take dried foods such as flake and micropellets, but this should not be relied upon.
Breeding
Darter Tetras have been bred in the home aquarium. A separate breeding tank should be set up with soft acidic water and plenty of thick clumps of fine leaved plants such as Java Moss. There should be good water movement, but ensure that the filter inlet is protected with sponge to prevent eggs/fry from being drawn in. A well conditioned pair should then be carefully acclimatised across. Spawning may be triggered by a slightly cooler partial water change, with the fish often spawning first thing the next morning. Once the female is spent of eggs, the pair should be removed from the spawning tank to prevent predation. The eggs (which may number around 150) should hatch within 36-48 hours, and once free-swimming, the fry can be offered infusoria followed by baby brineshrimp (Artemia nauplii) as they grow.
