Can Fiddler Crab (Brackish) and Silver Arowana Live Together?
Fiddler Crab (Brackish) and Silver Arowana are not recommended as tank mates due to incompatible water types. Housing these species together is likely to result in stress, health problems, or direct harm to one or both fish.
At a Glance
Behaviour & Temperament
Fiddler Crab (Brackish) is a generally mild-mannered species (3/10), while Silver Arowana is moderately assertive (6/10). This modest difference means Silver Arowana may occasionally assert dominance over Fiddler Crab (Brackish).
In terms of spatial distribution, Fiddler Crab (Brackish) prefers the Bottom (Substrate) zone, whereas Silver Arowana occupies the Top (Surface) zone. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.
Worth noting: Silver Arowana is a known jumper, so a tight-fitting lid is essential.
Water Parameters
The safe temperature window for both species falls between 24°C and 30°C. Aim for the midpoint of this range (around 27.0°C) for optimal comfort.
Both fish can tolerate a pH between 7.5 and 7.5. Maintaining a stable value within this band is more important than hitting an exact number.
For general hardness, the shared comfort zone is 10–12 dGH. Regular testing will ensure conditions stay within this range.
Crucially, these species require different water types — one needs freshwater while the other requires brackish conditions. This is a hard barrier to keeping them together. An aquarium test kit is recommended for monitoring.
Tank Setup
To house Fiddler Crab (Brackish) and Silver Arowana together, plan for an aquarium of at least 1200 litres with a minimum length of 240 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.
Providing a mix of open swimming space and sheltered areas with rocks, driftwood, or plants will keep both species comfortable and allow natural behaviour.
Specific environmental needs for this combination include: Sand (Sifters), Driftwood (Digestion/Hiding), Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.
Both species do well with low (still water) water movement, so a standard filtration setup rated for the tank volume should suffice.
Find the right tank equipment
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Frequently Asked Questions
Can Fiddler Crab (Brackish) and Silver Arowana live together?▾
No. This combination is not recommended. Key incompatibilities — such as different water type needs — make cohabitation unsafe.
What size tank do Fiddler Crab (Brackish) and Silver Arowana need?▾
A minimum of 1200 litres (tank length at least 240 cm) is recommended. This provides enough space for both species to establish their own areas and reduces the likelihood of territorial disputes.
What water temperature is best for Fiddler Crab (Brackish) and Silver Arowana together?▾
Keep the aquarium between 24°C and 30°C. A target of around 27.0°C sits comfortably within both species' preferred ranges.
Are Fiddler Crab (Brackish) or Silver Arowana aggressive?▾
Fiddler Crab (Brackish) is generally mild-mannered (3/10) and Silver Arowana is moderately assertive (6/10). Their similar temperaments generally lead to a peaceful coexistence.
What pH do Fiddler Crab (Brackish) and Silver Arowana need?▾
Both species overlap in the 7.5–7.5 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.
How do I manage Silver Arowana's territorial behaviour?▾
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Silver Arowana space to claim a territory without encroaching on the other fish's area. Adding décor that divides the tank into distinct zones works especially well.
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