GYMNOTHORAX POLYURANODON FRESHWATER TIGER MORAY EEL MEDIUM

🐍 Gymnothorax polyuranodon — Freshwater Tiger Moray Eel Care Guide

Gymnothorax polyuranodon, commonly known as the Freshwater Tiger Moray Eel, is a fascinating, snake-like predator native to Southeast Asia and Oceania. Known for its vivid yellow patterning and fierce reputation, this moray is one of the few eel species found in low-salinity environments. Despite the “freshwater” label, this species thrives best in brackish to lightly marine conditions, and its care requires attention to water chemistry, tank security, and feeding behavior. This species is not for beginners but can be incredibly rewarding for experienced aquarists looking for something bold and unique.

🌍 Natural Habitat

• Native Range: Indonesia, Papua New Guinea, the Philippines, and surrounding islands

• Habitat: Estuarine rivers, tidal mangrove swamps, and coastal streams

• Water Type in the Wild: Primarily brackish, occasionally entering freshwater for short durations

• Substrate: Mud, sand, or silt with dense root systems and crevices for hiding

🏡 Aquarium Setup

• Minimum Tank Size: 75 gallons for juveniles; 125+ gallons required for adults

• Tank Shape: Long tanks are preferred over tall ones to accommodate length and movement

• Substrate: Fine sand or smooth gravel to prevent damage to the eel’s delicate belly

• Decor:

  • Heavy use of caves, PVC tubes, driftwood, or rock structures for hiding

  • Cover is essential — this species is shy by day and exploratory at night

• Lid/Security: Escape artist! Tight-fitting, weighted or locked lid is mandatory

• Lighting: Low — indirect lighting preferred

• Filtration: Powerful external filter or sump with high biological capacity and low current

• Water Movement: Gentle flow — too much current stresses the eel

💧 Water Parameters

• Temperature: 75–82°F (24–28°C)

• pH: 7.4–8.4

• Salinity:

  • Juveniles: 1.005–1.010 SG (low-end brackish)

  • Adults: 1.010–1.018 SG (moderate brackish to light marine)

• Hardness: 10–20 dGH

• Ammonia/Nitrite: 0 ppm — highly sensitive to nitrogen waste

• Water Changes: 20–30% weekly with pre-salted, temperature-matched water

🍴 Diet and Feeding

G. polyuranodon is a strict carnivore and an ambush predator that prefers meaty, high-protein foods. Live prey is often required early on but can be transitioned to frozen.

• Preferred Foods:

  • Live or frozen shrimp, silversides, krill

  • Fresh tilapia, squid, or mussel meat

  • Earthworms or blackworms (great for juveniles)

• Feeding Behavior:

  • Feeds primarily at night

  • Use tongs to offer food near hiding spots

  • Will often refuse dry or pellet food

• Feeding Frequency:

  • Juveniles: 4–5 times per week

  • Adults: 2–3 times per week

• Caution: Uneaten food can foul water quickly — remove leftovers promptly

🧬 Temperament and Compatibility

• Behavior: Secretive, solitary, and ambush-oriented

• Disposition:

  • Shy when young, bold when comfortable

  • Will eat smaller tankmates if they fit in its mouth

• Tankmates:

  • Large, non-aggressive brackish fish (e.g., Monos, Scats, Archerfish)

  • Avoid slow-moving or bottom dwellers like gobies or puffers

• Best Alone? Often yes, or with one or two well-matched tankmates in a very large system

• Warning: May bite if handled or stressed — always use tools, not hands

🐣 Breeding Information

• Breeding in Captivity: Not documented

• Reproduction in Nature:

  • Spawns in the ocean; larvae drift in planktonic stages before returning to estuaries

  • True breeding requires marine conditions and is likely seasonal

• Conclusion: Not suitable for home breeding efforts

⚠️ Special Considerations

• Escape Risk: Known to squeeze through tiny gaps — secure every corner of the lid

• Brackish Water Is Necessary: Despite the name, this is not a true freshwater species

• Personality: Becomes more interactive and confident with age — some recognize their keepers

• Feeding Challenges: May need live food to start; patience is required to train onto frozen

📋 Quick Reference Summary

📝 Final Thoughts

The Freshwater Tiger Moray Eel is a rare and exotic species with a prehistoric look and sharp instincts. It demands specialized care, a brackish system, and secure housing — but in the hands of a capable aquarist, it becomes a show-stopping centerpiece. As it grows and gains confidence, its personality and boldness make it one of the most rewarding oddball fish to keep.