Red-eye Tetra
Bario sanctaefilomenae
Acestrorhamphidae
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About
The red-eye tetra is the plain silver characin with a blood-red half-ring above the pupil and a black-and-white tail base that has stood in shop tanks for decades. It has also just changed its name: recent work moved it out of Moenkhausia into the resurrected genus Bario, and FishBase, Wikipedia (citing the Catalog of Fishes) and Maidenhead Aquatics have all followed, while Seriously Fish still files it under Moenkhausia and notes that the whole genus sits in taxonomic limbo pending revision. Our diamond tetra moved too: the same break-up of Moenkhausia put it in Makunaima, so it is now Makunaima pittieri, in the same new family but a different subfamily. The two are still shelf neighbours — but because they both left the genus they shared, not because one of them stayed. Practically it is one of the easiest fish in the hobby: 7 cm, unbothered by anything from pH 6 to 8, and bred by the million in Eastern Europe and Asia. The caveat is temperament rather than water. Seriously Fish calls it a robust choice whose boisterousness can intimidate sedate fish such as anabantoids and dwarf cichlids, and says its fin-nipping reputation is usually fixed by a shoal of six to eight. Wikipedia is less forgiving: some individuals nip even in a group, and a fish kept alone is the most likely to.
Care
Six is the floor every source gives; eight to ten is what actually settles the nipping, and it is the number to use if anything in the tank carries long fins. Seriously Fish asks for 90 x 37.7 x 30 cm (106 litres) and Wikipedia says about 110 litres is normal, so roughly 110 litres over 90 cm of length. Plant the sides and back and leave the front open, because this fish spends the whole day crossing the tank. Water needs no work: 22-26 C, pH 6-8, 3-20 dGH covers ordinary tap water almost everywhere. It works the upper half of the tank, which is what makes it a good dither for peaceful medium-sized cichlids such as eartheaters and acaras. Keep the lid on, and keep slow veil-finned tankmates out.
Diet
Omnivore that takes worms, insects, crustaceans and plant matter in the wild. Dry food is accepted without fuss; add frozen or live daphnia, bloodworm and brine shrimp a few times a week, plus spinach or an algae-based flake for the vegetable share.
Tankmate compatibility
Gets along with (239)
Possible with care (129)
Avoid (50)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
What works for this species, most reliable first.
- Belly depthA hint only · only on well-fed adults, and only as a comparison
For most tetras, barbs and rasboras this is all there is: a conditioned female is deeper through the belly than a male of the same length.
Also in these lists
Similar species
Same category and the closest water parameters — if this species isn't quite it, start here.
Sold in Lithuania
These Lithuanian shops listed this species in their public catalogue (checked August 8, 2026). Stock moves — ask before you travel.
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Frequently asked questions
- What tank size does a Red-eye Tetra need?
- A Red-eye Tetra needs an aquarium of at least 110 litres (29.1 US gallons) with a footprint at least 90 cm (35.4 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Red-eye Tetra need?
- Red-eye Tetra does best at 22–28 °C (71.6–82.4 °F), pH 6–8 and a general hardness of 3–20 °dGH.
- What group size does a Red-eye Tetra need?
- Red-eye Tetra is a social species — keep a group of at least 6 so natural behaviour emerges and stress stays low.
- Is the Red-eye Tetra suitable for beginners?
- Yes — Red-eye Tetra is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.