Can Figure 8 Puffer (Brackish) and Goldfish (Comet / Common) Live Together?
Figure 8 Puffer (Brackish) and Goldfish (Comet / Common) 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 Goldfish (Comet / Common) is peaceful (1/10). This notable difference means Figure 8 Puffer (Brackish) may occasionally assert dominance over Goldfish (Comet / Common).
Large aggression gap (7 points) between Figure 8 Puffer (Brackish) and Goldfish (Comet / Common) increases stress risk for the more peaceful fish.
Figure 8 Puffer (Brackish) and Goldfish (Comet / Common) both frequent the Middle (Open Water) and Bottom (Substrate) region of the setup. This overlap can increase competition for space, so providing ample room and cover is important to keep both species comfortable.
Water Parameters
The safe temperature window for both species falls between 24°C and 24°C. Aim for the midpoint of this range (around 24.0°C) for optimal comfort.
Both fish can tolerate a pH between 7.5 and 8. Maintaining a stable value within this band is more important than hitting an exact number.
For general hardness, the shared comfort zone is 10–20 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 Goldfish (Comet / Common) together, plan for an aquarium of at least 240 litres with a minimum length of 120 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), Smooth Gravel (Sensitive Barbels). 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
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Frequently Asked Questions
Can Figure 8 Puffer (Brackish) and Goldfish (Comet / Common) 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 Goldfish (Comet / Common) need?▾
A minimum of 240 litres (tank length at least 120 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 Goldfish (Comet / Common) together?▾
Keep the aquarium between 24°C and 24°C. A target of around 24.0°C sits comfortably within both species' preferred ranges.
Are Figure 8 Puffer (Brackish) or Goldfish (Comet / Common) aggressive?▾
Figure 8 Puffer (Brackish) is semi-aggressive (8/10) and Goldfish (Comet / Common) 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 Goldfish (Comet / Common) need?▾
Both species overlap in the 7.5–8 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.
Will Figure 8 Puffer (Brackish) nip Goldfish (Comet / Common)'s fins?▾
Figure 8 Puffer (Brackish) is a known fin nipper. If Goldfish (Comet / Common) 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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