Ruby Tetra Care Guide - Aquarium Setup, Diet & Breeding

The Ruby Tetra is a minute characin with a slender, translucent body and a vivid ruby-red stripe that gives the species its common name. Depending on mood and lighting, the red coloration can extend from the head along much of the body, while the fins remain delicate and largely transparent. Its small size makes it an appealing choice for planted nano aquariums.

This is an active but peaceful schooling fish. In a suitable group, Ruby Tetras spend much of their time weaving through plants and open water, with the males often displaying to one another and showing stronger colour when they are excited or courting. They are less confident when kept singly or in very small numbers.

Axelrodia riesei is associated with small Colombian waterways, including quiet tributaries and forest-influenced habitats. Overhanging vegetation, submerged roots and leaf litter provide shelter and create a broken pattern of shade and open water, which suits the species' discreet, midwater lifestyle.

Ruby Tetras are sometimes confused with other tiny red characins, but their compact proportions and particularly fine, jewel-like appearance set them apart. They are best appreciated as a group, where their subtle social behaviour and flashes of colour become much more apparent.

Ruby Tetras are native to Colombia in northern South America, where they occur in the Río Meta basin and its associated tributaries. They come from warm, slow-moving tropical waters that may be clear, lightly stained or influenced by leaf litter.

A group of Ruby Tetras should have at least 40 litres, with a tank around 60 cm long by 30 cm wide providing a more useful footprint for swimming. Use gentle filtration and subdued flow, along with dense planting, fine-leaved stems, floating plants, roots and a few shaded areas. A dark, fine-grained substrate helps their colours stand out and resembles their natural surroundings; leaf litter can add shelter and gentle tannins when maintained appropriately. Keep the aquarium mature, stable and securely covered, as these tiny characins can jump.

Up to 2 cm (0.8 in) in adult length. Females are usually slightly larger and deeper-bodied than males, while males tend to remain slimmer.

Ruby Tetras are small omnivores that naturally pick at tiny aquatic invertebrates, insect larvae and other minute food items. Offer a varied diet of appropriately sized micro-pellets or crushed flakes supplemented with baby brine shrimp, daphnia, cyclops and other small frozen or live foods. Several modest feeds are preferable to large portions, and all food should be small enough for their tiny mouths.

Ruby Tetras are peaceful community fish and can be kept with similarly gentle, small species such as pygmy corydoras, small pencilfish, clown killifish, celestial pearl danios and other appropriately sized rasboras or tetras. They also work well with peaceful dwarf shrimp, although newly hatched shrimp may be eaten. Avoid large or boisterous fish, fin-nippers and predatory species, including angelfish, larger barbs, many larger gouramis and bigger cichlids, as these may intimidate or consume them.

Ruby Tetras are egg-scattering spawners that can breed in a separate, mature breeding aquarium with soft, slightly acidic water and subdued lighting. Condition a group with plenty of small live or frozen foods, then provide fine-leaved plants or spawning mops for the eggs. Remove the adults after spawning, as they may eat the eggs. The eggs usually hatch within a day or two, and the tiny fry should initially be offered infusoria or another suitably fine first food before progressing to newly hatched brine shrimp.

Females are generally a little larger and rounder through the abdomen, particularly when carrying eggs. Males are slimmer and often display more intense ruby colouring during courtship, although the difference can be subtle in young fish.