Alligator Gar

 

fish description – Alligator Gar Care Guide ($Atractosteus\ spatula$)

Category	Detail
Scientific Name	$Atractosteus\ spatula$
Common Name	Alligator Gar, Alligatorfish
Origin	Large rivers and floodplains of the Southern United States and Mexico
Adult Size	6–10 feet (2–3 meters)
Temperament	Highly Predatory, Solitary, Ambush Hunter
Lifespan	20–50+ years
Care Level	Expert/Public Aquarium Only (Immensely large and long-lived)

Export to Sheets

---

 

Appearance and Sexual Differences

 

• Short Description: A massive, torpedo-shaped fish with a thick, heavy body and a broad, short snout lined with two rows of large, sharp, fang-like teeth. Its body is covered in tough, protective, diamond-shaped ganoid scales.
• Coloration: Typically dark olive-green or brown on the dorsal surface, fading to yellowish-white on the belly. Juveniles may have dark spots and a dorsal stripe that fade with age. Sexing is generally impossible outside of mature breeding condition.
• Fins: Dorsal and anal fins are located far back on the body. They possess a highly vascularized swim bladder that functions as a lung, allowing them to breathe atmospheric air in low-oxygen water.
• Behavior: A sluggish, sit-and-wait ambush predator that spends much time floating near the surface or lying motionless near cover. Despite their size, they can strike prey with great speed.

---

 

Tank Requirements and Water Parameters

 

• Minimum Tank Size: Minimum thousands of gallons (ponds/public aquariums only). The absolute minimum for an adult is 10–12 feet in length and 4–5 feet wide.
• Schooling: Generally solitary. Can sometimes be kept with other very large, non-aggressive fish that are too big to be eaten.
• Temperature: Subtropical to Tropical range: $70^\circ$–$82^\circ\text{F}\ (21^\circ$–$28^\circ\mathrm{C})$. Tolerates a wide range, including brackish water.
• pH Level: Highly adaptable: 6.0 to 8.0. Requires massive filtration (sump systems, pond filtration) and frequent, very large water changes (up to 50% weekly) to maintain non-toxic conditions due to their immense bioload. Water flow should be moderate.
• Aquascape: Requires a soft sand substrate (or bare bottom) and ample open swimming space. Decor should be kept simple and minimal, with large, smooth driftwood or rocks used for cover.

---

 

Diet and Feeding

 

The Alligator Gar is a dedicated carnivore (piscivore) and opportunistic predator.

• Staple Diet: Primarily feeds on fish. Offer large whole fish (trout, smelt, tilapia—frozen and thawed), large prawns/shrimp, and other large crustaceans.
• Supplementation: Juveniles can be trained to accept meaty frozen foods and large carnivore pellets/sticks. Avoid feeding mammalian meat (beef heart, chicken) as the fat is indigestible and leads to organ damage. Eggs are poisonous and should never be consumed by humans or other pets.
• Schedule: Feed daily as juveniles. Adults require only one or two large meals per week.

---

 

Compatibility

 

• Caution: Extremely dangerous to any fish it can fit in its mouth. Due to its size and power, it is a risk to smaller tank maintenance equipment.
• Good Tank Mates: None suitable for typical hobby tanks. In massive systems, only the largest, non-aggressive, durable fish such as large Stingrays ($Potamotrygon$), Bichirs (large species), and Arowanas (large adults) can potentially co-exist.