Rubber Eel
Synbranchus marmoratus
The Rubber Eel (Synbranchus marmoratus) is a peaceful fish that's best left to experienced keepers. Give it a tank of at least 350 litres (92 US gallons), water held at 75-82°F, and a pH of 6-7.5.
Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.
Natural distribution
Central / South America
- South America
Regional colours match the stocking calculator's origin map.
Rubber Eel Tank Setup
Treat 350 litres (92 US gallons) as a starting point - big predators need length, strong filtration, and a secure lid. Hold the water at 75-82°F and pH 6-7.5, and assume anything small enough to swallow will eventually be eaten. They grow to around 60 cm, so plan the tank size and filtration for a full-grown adult rather than the small juvenile you see in the shop.
What Do Rubber Eels Eat?
They're meat-eaters, so feed good-quality frozen or gel foods rather than relying on generic flake. Go easy on portions - leftover protein fouls the water faster than plant foods do.
Rubber Eel Tank Mates
Not a true eel (swamp eel). Obligate air-breather and extreme escape artist - sealed lid essential. Will eat small fish. Needs large tank with soft substrate and hiding places. The Rubber Eel is peaceful, which is the first thing to weigh up when you choose tank mates. It's predatory, so anything small enough to fit in its mouth will be treated as food rather than a companion. Before you buy, run your full stocking list through our stocking calculator. It weighs temperament, adult size, and water needs together, which a single species page can't do on its own.
Are Rubber Eels Good for Beginners?
Not a sensible first purchase. Get the tank cycled, keep easier fish stable for a year, then revisit if you still want the extra work this species demands.
Rubber Eel - frequently asked questions
What size tank do Rubber Eels need?
Rubber Eels need a tank of at least 350 litres (92 US gallons). A bigger tank is always easier to keep stable, and gives them more room to settle in and behave naturally.
What water parameters do Rubber Eels need?
Keep them at 75-82°F with a pH of 6-7.5, steady rather than chased to an exact figure. In a cycled tank, ammonia and nitrite should both read 0 ppm, with nitrate kept low through regular water changes.
What do Rubber Eels eat?
Rubber Eels are meat-eaters. Feed good-quality frozen or gel foods rather than relying on generic flake, and don't overfeed. Feed small amounts once or twice a day, and remove anything they don't eat.
Are Rubber Eels good for beginners?
Rubber Eels are not a beginner species. They need precise conditions and consistent maintenance, so build experience with hardier fish before keeping them.
Common mistakes with Rubber Eels
- Underestimating tank size - the minimum footprint is 350 litres (92 US gallons); impulse buying into a smaller tank leads to stress and shortened lifespan.
Building a community? Run the full list through the stocking calculator before you add anything else.
Great tank mates
Chosen from temperament, overlapping temperature/pH bands, plausible minimum tank footprints, and size versus yours in App-aquatic data. Hobby nuance always wins - verify stocking and temperament before purchasing.
Check Rubber Eel against any other fish → Compares water parameters, predation risk, fin nipping and tank size, and draws both at life size.
Fish to avoid mixing with Rubber Eels
These well-known species are commonly sold alongside this fish but are not recommended tank mates - verify before purchasing.
- OscarPredator - Oscar will eat or injure smaller tank mates
- Zebra DanioFin nipper - will shred the fins of peaceful fish
- Clown LoachFin nipper - will shred the fins of peaceful fish
