Can Figure 8 Puffer (Brackish) and Marbled Hatchetfish Live Together?
Figure 8 Puffer (Brackish) and Marbled Hatchetfish 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
Figure 8 Puffer (Brackish) is a semi-aggressive species (8/10), while Marbled Hatchetfish is peaceful (1/10). This notable difference means Figure 8 Puffer (Brackish) may occasionally assert dominance over Marbled Hatchetfish.
Large aggression gap (7 points) between Figure 8 Puffer (Brackish) and Marbled Hatchetfish increases stress risk for the more peaceful fish.
In terms of spatial distribution, Figure 8 Puffer (Brackish) prefers the Middle (Open Water) and Bottom (Substrate) zones, whereas Marbled Hatchetfish 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.
Additional behavioural considerations to keep in mind: Aggressive fish may bully and stress shy, slow-moving species. Hyperactive swimmers can stress shy, slow-moving species through constant motion.
Worth noting: Marbled Hatchetfish 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 28°C. Aim for the midpoint of this range (around 26.0°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 Figure 8 Puffer (Brackish) and Marbled Hatchetfish together, plan for an aquarium of at least 72 litres with a minimum length of 60 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), Shells (Breeding/Hiding), Plants - Floating, Leaf Litter/Blackwater. Meeting these requirements will help both species thrive.
Both species do well with moderate (standard) water movement, so a standard filtration setup rated for the tank volume should suffice.
Find the right tank equipment
Browse tanks, décor, and equipment suited for this setup.
Frequently Asked Questions
Can Figure 8 Puffer (Brackish) and Marbled Hatchetfish live together?▾
No. This combination is not recommended. Key incompatibilities — such as different water type needs — make cohabitation unsafe.
What size tank do Figure 8 Puffer (Brackish) and Marbled Hatchetfish need?▾
A minimum of 72 litres (tank length at least 60 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 Figure 8 Puffer (Brackish) and Marbled Hatchetfish together?▾
Keep the aquarium between 24°C and 28°C. A target of around 26.0°C sits comfortably within both species' preferred ranges.
Are Figure 8 Puffer (Brackish) or Marbled Hatchetfish aggressive?▾
Figure 8 Puffer (Brackish) is semi-aggressive (8/10) and Marbled Hatchetfish is peaceful (1/10). The gap in aggression levels means the calmer fish may experience stress from the more assertive one.
What pH do Figure 8 Puffer (Brackish) and Marbled Hatchetfish 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.
Will Figure 8 Puffer (Brackish) nip Marbled Hatchetfish's fins?▾
Figure 8 Puffer (Brackish) is a known fin nipper. If Marbled Hatchetfish has long or flowing fins, there is a real risk of fin damage. Keeping Figure 8 Puffer (Brackish) in a larger group can help redirect nipping behaviour toward conspecifics.
How do I manage Figure 8 Puffer (Brackish)'s territorial behaviour?▾
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Figure 8 Puffer (Brackish) 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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