Redflank Bloodfin Tetra

About

Shops sell two 'bloodfin' tetras and the label rarely tells them apart. Aphyocharax rathbuni is the smaller of the pair: Seriously Fish gives 35-45 mm standard length for it against 50-55 mm for the ordinary bloodfin A. anisitsi, which this library already carries. It also carries more names than any small tetra needs - Seriously Fish heads its profile 'Green Fire Tetra, Rathbun's Bloodfin, Redflank Bloodfin, Rubinsalmler (DE)' - so the same fish arrives under four labels. The red sits low on the flank and in the anal and caudal fins over a body with a greenish metallic sheen, which is where 'green fire' comes from. Range separates them too: Seriously Fish calls A. rathbuni endemic to the Paraguay, Paraná and Uruguay drainages in Brazil, Paraguay, Argentina and Uruguay, while A. anisitsi is endemic to the Paraná drainage alone. And the ordinary bloodfin is the tougher fish of the two, tolerating 18-28 °C and pH 6.0-8.0 where A. rathbuni is given 20-26 °C and pH 6.5-7.5 - so the cool subtropical room that suits a bloodfin shoal is at the edge of what this one wants. One number to treat carefully: FishBase lists a maximum of 7.1 cm SL, far above every other published figure, and no aquarium source we could open corroborates a redflank that size. Seriously Fish's 35-45 mm and Fishipedia's 4-5 cm agree with each other, so we gate on 5 cm.

Care

Keep eight or more - Seriously Fish asks for at least six, and the extra fish are what keep its teeth off its neighbours - in a planted tank from 75 litres with at least 60 cm of length, open water down the middle and moderate flow, which Seriously Fish says it appreciates. Temperature 22-25 °C, pH 6.5-7.2, hardness anywhere from 2 to 20 °dGH, so ordinary Lithuanian tap water is no obstacle. The one real compatibility rule is stated plainly on that profile: pick robust, faster-moving tankmates, 'as this species has a reputation as a fin-nipper', and avoid long-finned fish - bettas, angelfish, veil-tailed guppies. Keep it covered; an active characin working the upper water leaves the tank through any gap it finds.

Diet

Unfussy omnivore that takes most aquarium foods. Flake and micro-pellets as the staple, with regular frozen or live daphnia, bloodworm and brine shrimp for colour and condition.

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.

These links are unpaid: we get nothing for them and ask for nothing.

Frequently asked questions

What tank size does a Redflank Bloodfin Tetra need?

A Redflank Bloodfin Tetra needs an aquarium of at least 75 litres (19.8 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Redflank Bloodfin Tetra need?

Redflank Bloodfin Tetra does best at 20–26 °C (68–78.8 °F), pH 6–7.5 and a general hardness of 2–20 °dGH.

What group size does a Redflank Bloodfin Tetra need?

Redflank Bloodfin Tetra is a social species — keep a group of at least 8 so natural behaviour emerges and stress stays low.

Is the Redflank Bloodfin Tetra suitable for beginners?

Yes — Redflank Bloodfin Tetra is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.

Sources

• Seriously Fish — Aphyocharax rathbuni (Green Fire Tetra, Rathbun's Bloodfin, Redflank Bloodfin)
• FishBase — Aphyocharax rathbuni (Redflank bloodfin)
• Fishipedia — Aphyocharax rathbuni
• Seriously Fish — Aphyocharax anisitsi (Bloodfin Tetra)