Moenkhausia sanctaefilomenae

Red-eye Tetra

Classification

Characidae

Distribution

Brazil, Paraguay and Argentina. You’re unlikely to see any wild fish for sale though. Due to its popularity, it’s commercially bred in huge numbers for the trade. Most of the ones on sale in the UK originate from Eastern Europe.

Habitat

Mostly inhabits clear water rivers that feed the famous Pantanal wetlands. Unlike in the often murky waters that flow through the Amazon rainforest, aquatic vegetation grows densely here. Massive rafts of floating plants such as Eichhornia and Salvinia occur frequently. Submerged species include various Echinodorus, better known as ‘Amazon’ sword plants (an odd common name as they don’t occur in the Amazon itself). These grow in huge beds in some of the areas where M. sanctaefilomenae can be found.

Maximum Standard Length

2.8″ (7cm).

Aquarium SizeTop ↑

It’s a particularly active species and given its adult size deserves a tank of at least 36″ x 15″ x 12″ (90cm x 37.7cm x 30cm) – 106 litres.

Maintenance

Quite an adaptable species that will thrive in most well maintained tanks, although it doesn’t like very brightly lit or sparsely decorated environments. It looks excellent in a densely planted tank.

It can also be kept in an Amazonian biotope setup if you wish. Use a substrate of river sand and add a few driftwood branches (if you can’t find driftwood of the desired shape, common beech is safe to use if thoroughly dried and stripped of bark) and twisted roots. A few handfuls of dried leaves (again beech can be used, or oak leaves are also suitable) would complete the natural feel. Aquatic plants are not a feature of this species‘ natural waters. Allow the wood and leaves to stain the water the colour of weak tea, removing old leaves and replacing them every few weeks so they don’t rot and foul the water. A small net bag filled with aquarium-safe peat can be added to the filter to aid in the simulation of black water conditions. The lighting should be fairly dim.

Water Conditions

Temperature: 72 to 79 °F (22 to 26°C)

pH: Due to the great range of water conditions between the wet and dry seasons in its natural waters, it's quite unfussy and will do well anywhere in the pH range 6.0-8.0

Hardness: 3 to 20°H

Diet

Easy to feed. It will readily accept just about anything offered. For the best condition and colours offer regular meals of small live and frozen foods such as bloodworm, Daphnia and brine shrimp, along with dried flakes and granules. Some vegetable matter should also be included in the diet. Try spinach leaves or a good quality algae based flake.

Behaviour and CompatibilityTop ↑

A decent, albeit robust choice for the ‘general’ community tank, where it will add plenty of movement. Sedate species such as anabantoids or dwarf cichlids can be intimidated by its somewhat boisterous nature,so it’s best kept with active tankmates. Other similarly sized tetras, rainbowfish, larger rasboras, barbs and most danionins make excellent choices. Bottom dwellers such as Corydoras catfish, Doradids, small Loricariids and botiine loaches are also good companions. It can also be used as a dither for non-aggressive, medium-sized cichlids.

Although it has a reputation as a bit of a fin nipper, this behaviour can usually be rectified by keeping it in a small shoal of at least 6-8 specimens. When maintained in these kind of numbers any squabbling is generally contained within the group. As with virtually all tetras, it fares better in the presence of conspecifics anyway, and tends to be a little skittish if kept in insufficient numbers.

Sexual Dimorphism

Female is a rounder bodied fish when inbreeding condition.

Reproduction

Can be spawned in a similar way to other species in the genus. You’ll need to set up a separate tank in which to do so, if you want to raise fry in any great numbers. Something around 18″ x 12″ x 12″ in size is fine. This should be very dimly lit and contain clumps of fine-leaved plants such as java moss or spawning mops, to give the fish somewhere to deposit their eggs. Alternatively you could cover the base of the tank with some kind of mesh. This should be of a large enough grade so that the eggs can fall through it, but small enough so that the adults cannot reach them. The water should be soft and acidic in the range pH 6.0-7.0, gH 1-10, with a temperature of around 80-84°F. A small air-powered sponge filter bubbling away very gently is all that is needed in terms of filtration.

It can be spawned in a group, with half a dozen specimens of each sex being a good number. Condition these with plenty of small live foods and spawning should not present too many problems.

Alternatively it can be spawned in pairs. Under this technique the fish are conditioned in male and female groups in separate tanks. When the females are noticeably full of eggs and the males are displaying their best colours, select the fattest female and best-coloured male and transfer them to the spawning tank in the evening. They should spawn the following morning.

In either situation the adults will eat the eggs given the chance and should be removed as soon as eggs are noticed. These will hatch in 24-36 hours, with the fry becoming free swimming a 3-4 days later. They should be fed on an infusoria–type food for the first few days, until they are large enough to accept microworm or brine shrimp nauplii.

NotesTop ↑

This species can be found swimming in most dealers’ tanks and is one of the best choices for the newcomer to fishkeeping. All the fish sold in the trade have been captive bred and as such are unfussy regarding water chemistry and diet.

The taxonomic status of all species in the genus Moenkhausia is currently Incertae Sedis, meaning uncertain. The genus is currently used as something of a catch-all for a large number of small characin species. Most experts agree that a full revision is required, with the likely outcome that many of these will be placed into new or different genera.