Breeding Rummy-Nose Tetra
How to breed Hemigrammus rhodostomus, an egg-scattering tetra: sexing, conditioning, soft acidic spawning setup, hatch time and the demanding fry care.
Overview
Hemigrammus rhodostomus is an egg-scattering characin that offers no parental care. Its breeding difficulty is rated advanced: success depends on consistently soft, acidic water and managing the slow-growing fry. Seriously Fish notes the adults will eat the eggs if they are not removed promptly after spawning.
Sexing
According to Seriously Fish, mature females are noticeably rounder in the body than males, which is the most reliable external difference. Gender identification is otherwise difficult unless a female is obviously gravid.
Conditioning the Breeders
Condition the fish with plenty of small live foods before attempting to spawn them. Reproductive capability depends on the parents having been kept in soft, acidic water throughout their lives; persistently high mineral content can render breeders sterile. Keep conditioning fish under dim lighting for several days before introducing them to the spawning tank.
Breeding Setup
- Separate breeding tank, roughly 18 x 10 x 10 inches, with very dim lighting
- Fine-leaved plants (java moss) or spawning mops, or a mesh base so eggs fall out of reach of the adults
- Soft, acidic water: pH 5.5-6.5, GH 1-5
- Temperature 80-84 F (27-29 C); peat filtration and RO water are beneficial
- Sterilise the breeding tank before use, as the eggs are highly prone to bacterial and fungal infection
Spawning Behavior & Trigger
Either group spawning (about six of each sex) or pair spawning of conditioned, sex-separated fish can be used; pairs are introduced once females are full of eggs. Seriously Fish reports that this species spawns almost exclusively in the evening.
Egg & Fry Care
Remove the adults as soon as eggs are seen. Eggs and early fry are light-sensitive, so keep the tank dark. Seriously Fish gives a hatch time of 24-36 hours, with fry becoming free-swimming 3-4 days later. The rummy-nose tetra is among the slowest-growing characins: fry need infusoria-grade foods for the first weeks before moving on to microworm and brine shrimp nauplii. Maintaining warm water for the early growth period is important for survival.
Common Challenges
The two main obstacles are achieving and holding suitably soft, acidic water and rearing the very slow-growing, light-sensitive fry. Egg fungus is common, so cleanliness in the breeding tank is essential.