The Silver Arowana (*Osteoglossum bicirrhosum*) is one of the most impressive freshwater fish that can be found in a home aquarium. Known as the “dragon fish” due to its archaic appearance, powerful body, and large scales, it consistently attracts the attention of aquarists worldwide. However, keeping this predator requires not just experience, but also a readiness to provide it with a truly colossal amount of living space. Before deciding to purchase a fry, it is necessary to realize that the arowana is not just a large fish; it is a fish that requires monumental conditions.
Silver Arowana: The Majestic “Dragon Fish” – An Overview and Why It Needs Space
The Silver Arowana is a representative of the Osteoglossidae family and originates from the Amazon, Essequibo, and Orinoco river basins in South America. In the wild, this fish reaches impressive sizes, often exceeding 90 centimeters. In an aquarium, with proper care, it also grows very large, typically reaching 60–80 centimeters.
The main reason why the arowana needs a huge aquarium lies in its biology and swimming style. It is a pelagic (inhabiting the water column) predator accustomed to the endless space of tropical rivers. It doesn’t just swim; it patrols its territory, making sharp, long dashes. Restricting its movement in a confined space leads to serious physical and psychological problems.
- Maximum Size: Up to 90–100 cm in the wild.
- Growth Rate: Grows very rapidly in the first few years of life, sometimes gaining 5–10 cm per month.
- Swimming Style: Requires a long, straight trajectory for turning and acceleration.
Biology and Behavior of the Silver Arowana: What to Know Before Buying
Understanding the arowana’s behavior is critically important for planning its habitat. It is a territorial and dominant fish that spends most of its time near the water surface, hunting for prey. Its unique ability is to jump out of the water to catch insects and small animals, which requires an absolutely secure aquarium lid.
Behavioral Features Affecting Tank Size:
Sudden Movements. An arowana can be startled by sudden noise or movement near the aquarium. In a panic, it begins to thrash about, which in a small aquarium inevitably leads to injuries – damage to scales, fins, or, worse, collisions with the walls and bottom. This phenomenon is called “arowana psychosis” or “arowana frenzy” by aquarists.
Spatial Orientation. The arowana needs sufficient space to maneuver to avoid constant friction with walls and decorations. Constant turns in a confined space cause spinal curvature and fin deformities, which irreversibly affect health.
Jumping Ability. As mentioned, arowanas are excellent jumpers. A minimum aquarium height and a securely fixed lid are non-negotiable requirements. The lid must be heavy so that the fish cannot move it.
Minimum Aquarium Volume for Silver Arowana: Calculating Space
Experts strongly advise against purchasing a Silver Arowana if you cannot provide it with an aquarium of at least 800 liters. However, in the case of the arowana, volume is a secondary parameter. The length and width of the aquarium are much more important.
Volume and Dimensions Requirements
The calculation of minimum aquarium dimensions for an adult arowana (60–80 cm) should be based on its body length.
- Minimum Aquarium Length: Should be at least 3–4 times the fish’s body length. If the arowana grows to 70 cm, the aquarium length should be 210–280 cm. The absolute minimum is 250 cm.
- Minimum Aquarium Width: Should be at least 1–1.5 times the fish’s body length so it can turn comfortably. A minimum of 80–100 cm.
- Minimum Aquarium Height: Although the arowana swims near the surface, the height (minimum 70–80 cm) is important for stabilizing water volume and preventing jumps.
Thus, an aquarium with a capacity of 800–1000 liters, but with dimensions of 250x80x70 cm (LxWxH), is the basic requirement for keeping one adult specimen of Osteoglossum bicirrhosum.
Table of Minimum Volume Requirements
| Arowana Age/Size | Minimum Volume (Liters) | Minimum Length (cm) | Note |
|---|---|---|---|
| Fry (up to 20 cm) | 300–400 | 150 | Temporary housing, immediate upgrade required. |
| Juvenile (20–40 cm) | 600–800 | 200 | Requires constant growth monitoring. |
| Adult (60–80 cm) | 1000+ | 250–300 | Optimal conditions for longevity. |
Important: Never buy an arowana hoping it “won’t grow” in a small volume. This will lead to a shortened lifespan, illness, and suffering for the fish.
Why Arowanas Need Large Aquariums: The Importance of Space for Health and Comfort
Providing the arowana with sufficient space directly impacts its physiological and psychological state. In a cramped aquarium, the fish doesn’t just feel discomfort; it gets sick.
1. Water Parameter Stability
Large fish produce a huge amount of waste. In a small volume, the concentration of nitrates, nitrites, and ammonia rises catastrophically fast, even with frequent water changes. A large water volume acts as a buffer, smoothing out sharp chemical parameter spikes.
- Nitrogen Cycle: The larger the volume, the easier it is to control toxic nitrogen compounds.
- Temperature Regime: Large water volumes change temperature more slowly, which is critically important for tropical fish.
2. Prevention of Physical Deformities
The most common problems caused by confinement are:
- Spinal Curvature: Constant turns in a confined space.
- Ptosis (Drooping Eyes): Although the exact causes of ptosis are still debated (often linked to diet or reflections on the bottom), in narrow aquariums, the fish often looks down in search of food or reflections, which can exacerbate the problem.
- Fin Erosion: Constant friction against walls and decorations.
3. Stress Reduction
The arowana is a fish that requires a calm environment. Stress caused by confinement leads to a weakened immune system and susceptibility to infections. Only in a spacious aquarium does it exhibit its natural, majestic behavior.
Equipment for a Large Arowana Aquarium: Filtration, Aeration, and Lighting
An aquarium for an arowana is not just a large glass box; it is a complex, powerful life support system. The equipment should be rated for volumes 2–3 times the nominal aquarium volume.
Filtration
Arowanas are messy fish. An oversized, double or triple filtration system is necessary, focused on mechanical cleaning and biological waste processing.
- External Canister Filters: It is recommended to use two powerful external filters (e.g., Eheim Professional or Fluval FX series), each rated for a volume of 1000+ liters.
- Sump: For aquariums of 1000+ liters, a sump is the best solution, providing maximum biological filtration and stability.
- Powerful Mechanical Pre-filter: To remove large food particles and excrement, preventing clogging of the main filter.
Heating and Aeration
Arowanas require a stable tropical temperature (24–30°C). In large aquariums, multiple heaters should be used to avoid localized overheating and ensure even heat distribution.
Aeration should also be enhanced, as the high biological load requires a large amount of dissolved oxygen.
Lighting and Lid
Lighting is usually not critical if the aquarium does not contain demanding plants. However, the lid is a matter of life and death for the fish.
The lid must be:
- Super Strong: Made of thick glass or acrylic.
- Heavy and Secured: Reliably fixed or have sufficient weight so that the fish cannot move it when jumping up to 1 meter high.
- Gap-Free: Even a small gap around wires or feeding areas can become an escape route.
Silver Arowana Compatibility with Other Fish: Who Can Be a Tankmate in a Spacious Aquarium?
The Silver Arowana is a predator. Anything that fits into its mouth will be eaten. Its mouth is wide enough to swallow a fish up to one-third of its own length.
Compatibility is only possible in very large aquariums (1500+ liters) provided that the tankmates have a similar temperament but differ in swimming style and size.
Potential Tankmates (if size is appropriate):
- Large Catfish: Redtail Catfish (*Phractocephalus hemioliopterus*) or Plecostomus (*Pterygoplichthys gibbiceps*) – they inhabit the bottom and do not compete for the upper water layers.
- Rays: Freshwater Stingrays (*Potamotrygonidae*) – also occupy the lower tier.
- Large Cichlids: Guapote (*Nandopsis managuensis*) or Oscar (*Astronotus ocellatus*), if they are large enough that the arowana won’t eat them, and the aquarium is large enough to reduce territorial aggression.
- Pacu (*Piaractus brachypomus*): Large, peaceful fish that can accompany an arowana in giant tanks.
Golden Rule of Compatibility: If a fish is less than half the length of the arowana, it will be considered food. If the aquarium is less than 1500 liters, it is better to keep the arowana in a species-only tank.
FAQ: Answers to Frequently Asked Questions About Arowana Aquarium Volume
Does a Small Volume Affect an Arowana’s Growth?
Yes, but not in the way beginners think. The fish doesn’t stop growing; it slows down, which is called “stunting.” This is not a healthy state but a pathology caused by stress and the accumulation of growth hormones in the water. A stunted arowana looks disproportionate, has a shortened body, and lives significantly less.
Can a Fry Be Kept in a 200-Liter Aquarium?
Fry (up to 15 cm) can be kept in a 200–300 liter aquarium, but only for up to 3–4 months. This is a temporary measure. By the time the fish reaches 25–30 cm, it already needs an aquarium at least 180 cm long (about 600 liters). You should always plan for an adult specimen.
What is the Minimum Acceptable Aquarium Width?
The width of the aquarium (depth from the front glass to the back) should be as large as possible. For an adult arowana, 70 cm is a critical minimum, 80–100 cm is a comfortable standard. A narrow aquarium is the most common cause of injuries during sharp turns.
Does an Arowana Aquarium Need Substrate?
Substrate is not mandatory, and many professionals prefer a bare bottom for easier cleaning. If substrate is used, it should be coarse so that the arowana cannot swallow it along with food. Having ample free swimming space is more important than complex decorations and substrate.
Interesting Facts About the Silver Arowana: From Legends to Modern Aquaristics
The Silver Arowana, like its Asian relatives (e.g., the Asian Arowana, Scleropages formosus), is surrounded by many myths and legends related to its appearance and longevity.
- Living Fossil: Arowanoids are considered among the oldest fish species, having survived practically unchanged since the time of dinosaurs.
- Symbol of Luck: In Asian culture, arowanas, especially red and golden species, are considered symbols of wealth, prosperity, and protection from evil spirits. The Silver Arowana, although less expensive, also carries positive symbolism.
- Unique Breeding Method: Arowanas are “mouthbrooders.” The male incubates the fertilized eggs, and then the fry, in his mouth for several weeks until they are large enough to survive on their own.
- Long-Livers: Under ideal aquarium conditions and a balanced diet, the Silver Arowana can live for 10–15 years, and sometimes longer.
Keeping a Silver Arowana is a serious commitment that requires significant investment in volume and equipment. However, the reward will be observing one of the most majestic and graceful freshwater fish, which, with proper care, will delight the aquarist for many years.