Thac Ba spiny eel

Where they come from

Thac Ba spiny eels are from northern Vietnam, named after Thac Ba Lake. Think flooded valleys, rocky margins, and pockets of soft sand between roots and stones. The water tends to be on the softer side with leaf tannins, and flow varies from calm coves to gentle currents.

Setting up their tank

Give them room. An adult hits the size of a hefty sub sandwich, so a 4-foot tank (55-75 gallons) for one is my floor. Bigger is better if you want a group. Tight lid is non-negotiable. They are expert escape artists and will find any gap around cables or the filter.

• Substrate: fine sand, at least 2 inches. They like to bury with just the snout sticking out. Skip sharp gravel.
• Hides: driftwood tangles, PVC or bamboo tubes, rock piles with sand underneath. Give them several choices.
• Lighting: on the dimmer side. Floating plants help them feel bolder.
• Filtration: strong biofiltration with gentle to moderate flow. Add a pre-filter sponge on the intake so they do not get their face stuck.
• Heater: stable 75-82 F (24-28 C). Use a heater guard or an external/inline heater so they cannot burn themselves while wedged under it.

Water numbers that have worked for me: pH 6.5-7.5, soft to medium hardness. Keep it clean and oxygenated. They sulk and go off food if nitrates creep high, so aim for regular 25-30% weekly water changes.

What to feed them

They hunt by smell, not sight. New arrivals usually want live or moving foods at dusk. Earthworms (cut for smaller eels), blackworms, bloodworms, chopped prawn, and small snails get them going. Once they settle, most can be taught to take frozen and even soft sinking sticks.

• Staples: chopped nightcrawlers, blackworms, frozen bloodworms, mysis, prawn/shrimp, tilapia slivers.
• Extras: live snails (for enrichment), insect larvae, thawed mussel or clam.
• Dry foods (after training): soft sinking carnivore sticks or pellets.

Feed smaller amounts 4-5 times a week. They overeat fast and get gut issues. I like to add a vitamin soak to frozen foods once or twice a week, especially for wild fish coming out of quarantine.

How they behave and who they get along with

They are shy at first, mostly active at dusk. Give them cover and they relax. Mine spends mornings buried with just the snorkel-nose out, then cruises the bottom at lights out. They are not bullies, but they are predators. If a fish can fit in that tube mouth, it is a snack sooner or later.

• Good tankmates: medium rainbows, larger rasboras, peaceful barbs that are not nippy, robust tetras too big to swallow, calm gouramis, and non-pushy cichlids like severums (watch personalities).
• Use caution: loaches and fast bottom feeders will outcompete them at dinner. Feed the eel by tongs so it gets its share.
• Avoid: tiny fish (neons, endlers), fin nippers, very aggressive cichlids, and spiny or spiky fish they might try to eat.

You can keep one, or a small group if the tank is big and there are lots of hides. In cramped quarters, they bicker with body shoves, but with space they mostly ignore each other.

Breeding tips

Real talk: hobbyist reports of breeding this species are basically unheard of. Farms use hormones with spiny eels. If you want to experiment, think very large tank, soft warm water, tons of cover with fine plants or mops, heavy feeding, and big cool-water changes to mimic rainy season. Females get rounder when full of eggs, but sexing is not obvious. If spawning does happen, they scatter eggs; remove adults right away. Do not be discouraged if nothing happens for months.

Common problems to watch for

• Escapes: most losses happen on night one. Seal every gap and keep the room floor dry and clear while they settle.
• Not eating: keep lights low, offer live worms first, and feed after lights out. Target feed with tongs so tankmates do not steal it.
• Internal parasites in wild-caught fish: skinny despite eating, white stringy poop. Quarantine and deworm under guidance. They are sensitive, so choose meds and dosing carefully.
• Ich and med sensitivity: they have reduced scales. Use gentler treatments and lower doses, add extra aeration, and avoid copper unless you know what you are doing.
• Injuries from decor: sharp rocks and coarse gravel scrape their skin. Switch to sand and rounded wood.
• Heater burns and filter mishaps: protect heaters and sponge the intakes.
• Water quality sulks: elevated nitrate makes them hide and refuse food. Increase water change frequency and clean the sand with a gentle siphon.