Aquaria/Rummy-nose tetra

From Wikiversity
Jump to navigation Jump to search
Brilliant rummy nose 2.jpg

Rummy-nose tetras are small, freshwater, tropical fish often kept in aquaria. Three species are commonly called this name: Hemigrammus rhodostomus, Hemigrammus bleheri, and Petitella georgiae, but the latter two are called firehead tetra and false rummy-nose tetra, respectively.

Aquarium maintenance[edit | edit source]

The details of aquarium maintenance for all three species are more or less identical: they exhibit tight schooling behaviour both in the wild and in the aquarium. Consequently, they should be maintained in groups of no fewer than six individuals, with larger numbers being preferable where space permits. These tetras do best in a 25-gallon/80-litre aquarium. All three species are lovers of warm aquarium water; the temperature range for maintenance is 24 to 31°C, with temperatures as high as 33°C needed for breeding. Consequently, compatibility of these fishes with cooler-water fishes is contraindicated: for example, panda corydoras would be a bad choice of companion, as they prefer lower temperatures, with little overlap in the temperature ranges of the two species. Many fish can be kept with rummy-nose tetras, including smaller gourami, tetras, barbs, danios, Australian rainbows, and various catfish, such as Ancistrus. These fish cannot be kept with African cichlids as they have very different water parameters.

The water chemistry preferred by these fish, as might be inferred readily from that of the wild habitat, is soft, acidic water (hardness no higher than 6°H and pH around 6.4-7.0) though for maintenance purposes, the pH of the aquarium water can range from 5.6 to 7.4. However, if captive reproduction is to be attempted, the rummy-nose tetra needs' soft, acidic water, as high levels of calcium ions in the water induce sterility in these fishes. A planted aquarium is welcomed by these fishes, particularly if the plants include fine-leaved species such as Cabomba and Myriophyllum.

Feeding presents relatively few problems, as the fish will eagerly consume a range of prepared, as well as live, fish foods. In common with numerous other tetras, these fish particularly eat live bloodworms (the aquatic larvae of a midge of the genus Chironomus) and will also eat live Daphnia. Unlike those tetra species which adapt to surface feeding in the aquarium, rummy-nose tetras are not likely to add live mosquito larvae to their diets. They prefer to take their foods in the middle and lower regions of the aquarium.

Lifespan for the rummy-nose tetra in the aquarium is usually 5 to 6 years with careful maintenance. Exceptional specimens can live for more than 8 years.

The fish is interesting in that it can act as a "mine canary" in an aquarium, alerting the aquarist to potential pollution problems. When levels of certain metabolic wastes (ammonia, nitrites, and nitrates) exceed critical levels, the intense ruby-red colour of the fish's facial area becomes pale. They also become pale in appearance immediately after a water change, but in this instance, once clean water has been supplied, the intense deep red colour returns. Persistent paleness of the head is a sign that water chemistry parameters in the aquarium are in need of adjustment, and that pollutant levels may be dangerous for the inhabitants.

Reproduction[edit | edit source]

Brilliant rummy nose.jpg

Breeding rummy-nose tetras present serious challenges even for experienced aquarists, primarily due to two factors: the likelihood of sterility ensuing if the prospective parents are maintained in water with too high a level of dissolved calcium ions, and the slow growth rate of the fry. An additional problem is that gender differentiation is difficult by visual inspection alone, making pair selection partly a matter of luck unless an obviously gravid female is available for selection. Again, identical remarks apply to all three species listed above.

The breeding aquarium for the rummy-nose tetra, in addition, needs to be sterilised prior to use, as their eggs are notoriously sensitive to bacterial and fungal infection. Use of an antifungal agent is strongly advised once spawning is completed to prevent various fungi from attacking the eggs.

Parents must be maintained in soft, acidic water throughout their lives if they are to remain capable of reproduction. Failure to do so reduces chances of success from the very start. Furthermore, it is highly advisable to filter the water of the breeding aquarium over peat, or alternatively use one of the commercially available 'Blackwater Tonic' additives to provide the necessary chemical environment conducive to reproduction. Parent fish should, in addition, be conditioned heavily with copious live foods to bring them into prime breeding condition.

Though these fish prefer to spawn among fine-leaved plants, one problem is that the majority of fine-leaved plants available in the aquarium prefer high light levels (Cabomba is a particular case in point) while the rummy-nose tetra prefers to spawn under subdued lighting conditions. Workarounds for this include the use of Java moss (a plant that thrives even in very low light levels, and is an ideal spawning medium for many fishes) or the use of synthetic alternatives ("spawning mops" made of nylon are typically deployed where a suitable natural plant is unavailable).

The parents should be introduced to the breeding aquarium up to 7 days before spawning, fed heavily with live foods, and kept under subdued lighting. In addition, they tend to spawn under quiet conditions, thus the aquarium should be situated away from areas of busy human traffic. The temperature should be slowly raised to 32°C, and sometimes 33°C may be needed depending upon the individual specimens. Spawning is difficult to observe under subdued lighting, and while chase sequences followed by the adoption of a side-by-side position by the parents amid the provided spawning media may be taken as indication that spawning is indeed taking place, this is by no means certain. The judicious use of a low-power flashlight to observe spawning may be helpful in determining if eggs are actually being produced.

The species is not noted as a particularly egregious egg-eater (unlike, for example, the lemon tetras) but it is still advisable to remove the parents once spawning is completed. At this stage, antifungal agents to protect the eggs should be added, and indeed are vital in the case of this difficult, sensitive species.

Once spawning is completed, it is advisable to keep the aquarium under dim lighting conditions until the eggs have hatched and the fry are free-swimming. While rummy-nose tetras do not need their eggs to be kept in total darkness as is the case for neon and cardinal tetras, the eggs are known to exhibit some degree of photosensitivity, and subdued lighting is highly advisable during egg development in the breeding aquarium.

Development[edit | edit source]

Fertile rummy-nose tetra eggs take about 72 to 96 hours to hatch at 32°C. The fry spend a further 24 to 48 hours absorbing the yolk sac, when they become free-swimming. At this stage, the fry should be fed with infusoria or a special egg-layer fry food, and frequent partial water changes (around 10% of the aquarium volume every 24 to 48 hours) initiated.

The rummy-nose tetra presents another hurdle to successful captive reproduction - the fry are among the slowest-growing of all characins, and indeed among the slowest-growing of all popular aquarium fishes. Infusoria and other similar foods are required for the fry for a minimum of three weeks, and the fish may take as long as 12 weeks to migrate to larger foods; growth rates are particularly affected by temperature. Success at raising fry to a size where they are capable of taking larger food morsels is more likely to be achieved if the fry are kept at temperatures above 30°C for the first three months of life; even then, attrition rates due to diseases (most frequently bacterial infections) can be severe.

Up to six months ay be needed to raise fry to juvenile sizes, where they are capable of eating live daphnia on a regular basis. During this time, they are likely to be sensitive to sudden changes in water chemistry, and managing pollutants in the fry aquarium is made more difficult by the need to maintain low mineral content in the water during development to prevent sterility of the fish - the buffering capacity of the aquarium is likely to be low as a result of the low concentration of bicarbonate ions needed in addition to the low concentration of calcium ions. Taking all of these factors into account, the fish is a major breeding challenge for the aquarist.