The Rummy-nose Tetra is an elegant schooling fish with a vivid red head and striped tail, perfect for peaceful planted tanks with soft water.
Overview
Petitella rhodostomus is a small characin from the family Characidae, native to the clear-water tributaries of the Amazon River in Brazil. In the hobby, it is commonly known as the Rummy-nose Tetra, though this name is frequently a source of confusion since two other closely related species -- Hemigrammus rhodostomus and Hemigrammus bleheri -- are also sold under the same common name. Of the three, Petitella rhodostomus is considered the "true" Rummy-nose Tetra.
Adults reach 4.5--5 cm in length and live for 5--6 years with proper care. The fish's most striking feature is the intense red patch covering its head up to the gill covers, paired with a bold black-and-white pattern on the caudal fin. The body is silvery with a subtle greenish sheen. The intensity of the red coloration on the head serves as a reliable health indicator -- when stressed or exposed to poor water conditions, the red fades noticeably.
This is a schooling species that should be kept in groups of at least 8--10 individuals. In a large school, Petitella rhodostomus displays mesmerizing synchronized swimming, making it one of the most visually captivating schooling fish in the aquarium hobby.
Tank Requirements
A school of Petitella rhodostomus requires an aquarium of at least 80 liters. These fish are active swimmers in the middle water column, so it is important to leave plenty of open swimming space in the center of the tank without overcrowding it with decor.
Optimal water parameters:
- Temperature: 22--28 °C (comfort zone: 24--26 °C)
- pH: 5.5--7.0
- GH: 2--12 dGH
In the wild, these fish inhabit shaded stretches of rivers with soft, slightly acidic water stained by tannins. To replicate these conditions, use driftwood, dried oak or Indian almond leaves, and subdued lighting. Floating plants help diffuse the light, while Java fern, cryptocorynes, and Amazon swords provide shelter.
Filtration should be effective but without excessive current. An external canister filter with a spray bar to diffuse the flow works well. Aeration is essential -- Petitella rhodostomus prefers oxygen-rich water.
Feeding and Diet
Petitella rhodostomus is an omnivore with a preference for animal-based foods. In the wild, its diet consists primarily of small insects, their larvae, microcrustaceans, and detritus.
In the aquarium, it accepts most appropriately sized foods:
- Staple diet: high-quality flakes or micro-pellets for tropical fish
- Live and frozen foods: daphnia, cyclops, brine shrimp, bloodworms (small)
- Vegetable supplement: spirulina-based foods
To maintain the vivid red head coloration, foods enriched with carotenoids are particularly beneficial, along with regular feedings of live or frozen brine shrimp. Feed twice a day in small portions that the school consumes within 2--3 minutes. Overfeeding quickly degrades water quality, to which this species is especially sensitive.
Care and Maintenance
Despite a care level of 2 out of 5, Petitella rhodostomus demands stable water parameters. This fish is one of the best water quality indicators in the hobby -- at the slightest deviation in conditions, the red coloration on the head fades and the fish become lethargic.
Key care guidelines:
- Weekly water changes of 25--30% using conditioned or aged water
- Test water parameters at least once a week
- Vacuum the substrate with a gravel siphon during water changes
- Maintain stable temperature -- sudden shifts of even 2--3 °C can cause stress
This species is sensitive to elevated ammonia and nitrite levels, so it should only be introduced into a fully cycled aquarium with an established biological balance. It is not recommended to add Petitella rhodostomus to a newly set up tank.
Compatibility
Petitella rhodostomus is one of the most peaceful tetras, with an aggression level of 1 out of 5. It is an ideal inhabitant for a community aquarium with other calm species.
Excellent tank mates include:
- Small tetras: Neon Tetra, Cardinal Tetra, Black Neon Tetra, Glowlight Tetra
- Rasboras: Chili Rasbora, Scissortail Rasbora
- Bottom dwellers: Panda Corydoras, Sterbai Corydoras, Pygmy Corydoras
- Dwarf cichlids: Ram Cichlid, Cockatoo Dwarf Cichlid
- Small catfish: Bristlenose Pleco
Avoid keeping them with large or aggressive fish that may bully the school. Also avoid overly active tank mates, such as barbs, whose boisterous behavior can cause chronic stress in these delicate fish.
Breeding
Breeding Petitella rhodostomus in the home aquarium is moderately challenging (3 out of 5). The main difficulty lies in creating and maintaining the right water parameters for spawning.
To stimulate breeding, prepare a separate spawning tank of 30--40 liters with the following conditions:
- Temperature: 26--28 °C
- pH: 5.5--6.5
- GH: 1--4 dGH (very soft water)
- Dim or no lighting
- Fine-leaved plants (Java moss) or synthetic spawning mops on the bottom
Select a well-fed female with a rounded belly and the brightest-colored male. For 1--2 weeks prior to spawning, feed the breeding pair generously with live foods. Spawning typically occurs in the morning hours -- the female deposits up to 100--150 small eggs among the plants.
Remove the adults immediately after spawning, as they will readily consume their own eggs. The eggs hatch in 24--36 hours. For the first few days, the fry feed on their yolk sacs, after which they should be offered infusoria and microworms. After 7--10 days, they can be transitioned to baby brine shrimp. Fry grow slowly and require pristine water -- daily water changes of 10% are essential.