Among the most fascinating and mysterious marine fish, the Aeoliscus strigatus stands out immediately for its postural behaviour that is unique in the world: it swims in a vertical position, with its head towards the bottom and its tail towards the surface. This aspect, already incredible in itself, is accompanied by a tapered and translucent body, similar to a sharpened blade, which is why it is known as the razorfish.

Native to the warm waters of the Indo-Pacific, it belongs to the order of the Syngnathiformes, the same as seahorses and pipefish, with which it shares defensive strategies and an elongated morphology. But the razorfish possesses an entirely distinctive ecological and behavioural identity, which makes it interesting both for aquarists in search of unusual species and for marine biologists who study mimicry and group dynamics in reefs.

In the course of this article we shall explore every aspect of this extraordinary species: from biology to management in the aquarium, passing through reproduction, sexual differences and ecological interactions. Prepare to get to know one of the most surprising creatures of the tropical ocean 🌊.

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🐠 Common name

• Razorfish
• Vertical fish
• Blade fish
• Razorfish (English)

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🧾 Synonyms

• Centriscus strigatus (erroneous historical nomenclature)
• Often confused with Aeoliscus punctulatus or Centriscus scutatus
• Some commercial sources erroneously label it as “vertical pipefish”

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🔬 Morphology

The Aeoliscus strigatus has an extremely specialised morphology, the result of evolutionary adaptations rare among bony fish.

Morphological characteristics:

• Extremely narrow, rigid and translucent body
• Average length: 8–15 cm
• Scales modified into bony plates, similar to an exoskeleton
• Pronounced dorsal spine aligned with the dorsal fin
• Small mouth, turned forwards, suited to the capture of microfauna
• Very reduced pectoral and anal fins
• Variable colour: silvery with yellowish reflections, often with a longitudinal black line

In swimming, it assumes an almost perfectly vertical position, mimicking the branches of gorgonians or the tentacles of soft corals.

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♂️♀️ Differences between males and females

Sexual dimorphism is practically absent at the level of external morphology. However:

• Adult females can show a slightly fuller abdomen during the reproductive phase
• The males sometimes present more competitive behaviours in groups during mating
• In the laboratory, only dissections or hormonal analyses allow certain identification

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🧭 Way of life

In nature, the Aeoliscus strigatus lives in highly synchronised shoals, made up of dozens up to hundreds of individuals. Its gregarious behaviour is sophisticated and includes:

• Simultaneous collective movement in a vertical position
• Passive camouflage among the tentacles of gorgonians, soft corals or crinoids
• Perfect coordination in case of danger: the shoal closes up and moves as a single entity

The species is active during the day, and at night it takes refuge in the branches of madrepores, sheltered from predators.

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🚩 Territoriality

The Aeoliscus strigatus is not territorial in the classic sense. However:

• It defends the cohesion of the group
• It shows behaviours of exclusion towards individuals foreign to the shoal
• In the aquarium, it can show stress and passive aggressiveness if isolated or forced into unsuitable coexistences

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⏳ Life expectancy

• In nature: 4–6 years, depending on predators and environmental conditions
• In the aquarium: 3–5 years with optimal management
  💡 In captivity, the duration of life is closely linked to the quality of the diet and the stability of the environmental parameters

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📏 Maximum size

• In nature: maximum 15 cm
• In captivity: it more commonly reaches 12–13 cm
• Slow but continuous growth until maturity

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🧬 Description

The body is as thin as a razor, completely compressed laterally. Its pointed head and semi-transparent colouring make the fish almost invisible if motionless among the gorgonians.
A unique distinctive feature is its permanent vertical posture, which differentiates it from every other coral reef species.

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📉 Status on the IUCN red list

Currently classified as “Least Concern” (LC) by the IUCN.
Reasons:

• Wide distribution
• No direct threat
• Low pressure from the ornamental trade
  But it could become vulnerable in the future because of the degradation of the coral habitats, especially in South-East Asia.

🌍 Habitat – origin and geographical distribution

Distributed throughout the tropical Indo-Pacific basin:

• Red Sea
• Indian Ocean (Maldives, Sri Lanka, Seychelles)
• Western Pacific (Philippines, Indonesia, Papua New Guinea)
• Australian Great Barrier Reef

Typical habitats:

• Shallow lagoons
• Inner slopes of the coral reefs
• Zones rich in gorgonians, crinoids or soft corals
• Depth: 1–40 metres, usually between 5 and 20 metres

🌡️ Temperature in nature

The Aeoliscus strigatus inhabits stable tropical and subtropical waters, where temperature is a key variable for the survival of the shoal.

• Optimal range: 24–28 °C
• Maximum tolerance: 22–30 °C, but already beyond 29 °C an increase in metabolic consumption and stress is observed
• Reduced activity below 23 °C
• Mimicry more active in the hottest hours of the day

Thermal stability is fundamental for the social cohesion of the group. Abrupt variations of temperature can lead to the break-up of the shoal.

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⚙️ Environmental parameters: nature vs aquarium

In order to keep an Aeoliscus strigatus successfully, it is essential to mimic the natural environmental conditions as closely as possible.

Parameter	In Nature	Recommended in the Aquarium
Temperature	24–28 °C	25–26.5 °C
Salinity	34–35 ppt	34.5–35 ppt
pH	8.0–8.3	8.2
Hardness (KH)	7–9 dKH	8–10 dKH
Nitrates	< 1 ppm	< 5 ppm
Phosphates	< 0.05 ppm	< 0.1 ppm
Oxygenation	High	Constant flow + skimmer

The conditions must be constant and free of rapid fluctuations, which the fish tolerates badly.

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🏠 Keeping in the aquarium

Keeping an Aeoliscus strigatus is possible and rewarding, but it requires experience and extreme attention to the social environment of the shoal.

✅ Fundamental requirements:

• A tank that is well established and biologically mature (6+ months)
• A minimum of 6 individuals in order to guarantee natural behaviour
• Realistic vertical decorations: artificial gorgonians, soft corals, resin branches
• Soft and diffused lighting
• Modest and continuous flow, without turbulence
• Carefully selected coexistences

⚠️ In the absence of other individuals of the same species or if introduced into inappropriate environments, it shows severe stress, anorexia and anomalous behaviours (such as spiral swimming or apathy).

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📐 Minimum dimensions of the aquarium

The Aeoliscus strigatus does not need large volumes, but it requires sufficient height and lateral space for coordinated swimming.

• Minimum volume: 150 litres
• Optimal: 250–300 litres with development in height (tanks 50 cm high or more)
• Sandy or fine bottom, in order to stimulate natural behaviour

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👥 Minimum population in the aquarium

You must keep it in a group. A shoal that is too small does not develop natural behaviours and can lead to:

• Feeding inhibition
• Chronic stress
• Loss of colour and mimicry

✅ Minimum recommended population: 6 specimens
Ideal: 8–12 individuals
In nature, the shoals even exceed 100 specimens, but in the aquarium a number between 6 and 12 guarantees behavioural stability.

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🤝 Compatibility with other species

It is a very peaceful fish, but easily intimidated or disturbed by companions that are too lively.

✅ Compatible with:

• Gobies
• Peaceful blennies
• Cleaner shrimps
• Quiet clownfish
• Cardinalfish
• Non-dominant anthias

🚫 To be avoided:

• Predatory or curious fish (Dottyback, Pseudochromis)
• Territorial fish (Tangs, large Angelfish)
• Fast and invasive fish (aggressive Chromis, active wrasses)

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🍽️ Feeding in nature and in the aquarium

In nature, the Aeoliscus strigatus feeds on:

• Zooplankton
• Planktonic crustaceans (copepods, isopods)
• Polychaete larvae
• Pelagic eggs
• Benthic microarthropods

In the aquarium, initially it is very selective, but it can adapt with patience.

Recommended diet in captivity:

✅ Live foods:

• Live artemia nauplii
• Live copepods
• Small mysids

✅ Frozen foods:

• Decapsulated Artemia salina
• Finely chopped mysis
• Cyclops

✅ Dry foods:

• Only if it has previously been got used to them. Use micro-granules suspended in the flow

🍽 Frequency: 3–4 meals a day, small and well distributed.

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💑 Reproductive behaviour

Reproduction has not been successfully observed in a domestic aquarium. In nature:

• The males do not possess brood pouches (unlike seahorses)
• Fertilisation is external
• The reproductive behaviour involves synchronisation and a collective dance in the shoal

The eggs are pelagic, transparent, suspended in the water for days before hatching.

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🐣 Protection of the fry

There is no parental care. The larvae are planktonic and rarely survive in an aquarium:

• They need live microplanktonic food
• They require isolated and stable environments
• They rarely develop in community tanks

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🔀 Risks of hybridisation

Currently there are no documented cases of interspecific hybridisation for Aeoliscus strigatus.
Despite the similarity with A. punctulatus, the reproductive barriers appear to be effective.

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💪 Hardiness

It is a delicate fish at the beginning, but it becomes very stable if acclimatised correctly:

• It requires stable parameters
• Sensitive to swings of temperature and salinity
• It reacts badly to solitude or to noisy tanks
• Very vulnerable to intestinal parasites and gill flagellates

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💡 Lighting in the aquarium

It requires diffused, natural, not intense light. It prefers zones:

• With shade
• With cover from soft corals or artificial branches
• Lighting from light units with a wide spectrum (6500–10000 K)

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🌬 Current in the aquarium

It must be gentle and laminar, never direct or turbulent. The ideal:

• Parallel and constant flow
• Directed diagonally, simulating the lagoon environment
• Low-flow pumps, alternating in order to imitate the tide

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🛒 Availability in the trade

Present in the specialist trade, but not always easy to obtain. Often available to order.

💰 Price: 30–60 € per specimen, higher for groups
🔍 Pay attention to correct identification: many are confused with A. punctulatus.

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✅ Pros and Cons

✔️ Advantages

• Unique aesthetics
• Spectacular behaviour
• Gregarious and peaceful
• Reef-safe
• Rare visual interaction for visitors

❌ Disadvantages

• It requires a group
• Complex diet at the beginning
• Sensitive to stress and environmental changes
• Difficult to obtain

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🧰 PRACTICAL BOXES

Recommended acclimatisation

• Method: slow drip for 2 hours
• Introduction with low light
• No noises or sudden movements
• First feeding within 4–6 hours

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Weekly routine

Day	Morning	Evening
Monday	Live artemia	Copepods
Tuesday	Cyclops	Chopped mysis
Wednesday	Fasting	Decaps. artemia
Thursday	Copepods	Mysis + gel
Friday	Live artemia	Mysis + Cyclops
Saturday	Copepods	Fasting
Sunday	Mixed gel	Live artemia

❓ FAQ

1. Can I keep only one Aeoliscus strigatus?
No. It lives in shoals. A single individual develops severe stress and dies within a few weeks.

2. Is it compatible with corals?
Yes, it is totally reef-safe.

3. What is the main difficulty in keeping it?
Adaptation to feeding and the need for a group.

4. Can I keep it with wrasses or chromis?
Only if they are not hyperactive or territorial.

5. How do I understand whether it is well?
It swims in a group, feeds actively and maintains a stable vertical posture.

6. Does it eat dry feed?
In rare cases. It prefers live or frozen. The adaptation is long.

7. Is it suited to beginners?
No. It requires experience and knowledge of feeding and behavioural flows.

8. Which layout is most suitable?
A tank with artificial gorgonians, developed height, shaded zones and low turbulence.

9. How long can it live in an aquarium?
Up to 5 years if maintained correctly.

10. Where can I buy it?
At retailers specialising in exotic marine fauna. Avoid online purchases without guarantees.

11. Can I keep it with shrimps?
Yes, it is compatible and often ignores them completely.

12. Can I keep two shoals of Aeoliscus in a tank?
No. They merge or they compete. Better a single homogeneous shoal.

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🧠 Conclusion

The Aeoliscus strigatus is not just any fish. It is a biological work of art, a model of mimicry, gregarious behaviour and morphological evolution. Inside the marine aquarium, it offers spectacle, harmony and amazement. But it does not forgive mistakes.

If you are ready to offer it a group, a stable environment, careful feeding and spaces consistent with its nature, then you will be able to enjoy one of the rarest and most memorable aquarium experiences.

It is not just a vertical fish. It is a fish that changes your perspective.