Moluccas snake eel

Where they come from

Moluccas snake eels (Yirrkala moluccensis) come from the Indo-Pacific around Indonesia and nearby areas. They are the kind of eel you find tucked into sand or rubble slopes, with just the head poking out waiting for food to drift by.

That background tells you basically everything about how to keep them: give them somewhere to bury, keep the tank calm and stable, and plan around an ambush predator that would rather hide than cruise around like a moray.

Setting up their tank

This is an expert fish mostly because of escape risk and because they do not tolerate sloppy setups. You want a mature marine tank with stable salinity and temperature, and you want to design the whole scape around an eel that lives in the substrate.

• Tank size: I would not bother under 75 gallons, and bigger is easier if you plan tankmates. They can get longer than you think.
• Substrate: fine sand, deep enough that they can bury comfortably. Think 3-4 inches as a starting point.
• Rockwork: stable, sitting on the glass or on a support before sand goes in. They will dig and undermine things.
• Flow: moderate. They like oxygenated water but not a sandstorm.
• Filtration: strong skimming and plenty of bio capacity. They are messy eaters once they settle in.
• Lighting: whatever suits the rest of the system. They do not care, but they do appreciate shade and overhangs.

I have had the best luck giving them at least one "home" area: a sandy pocket next to a rock ledge or a length of PVC buried under the sand with one end exposed. They will still bury, but having a predictable spot makes feeding and checking on them way less stressful.

What to feed them

They are meaty carnivores. Mine took food best once it learned the feeding routine and realized the tongs were not a threat. Early on, they can be shy and only eat after lights out.

• Best staples: raw shrimp, squid, clam, scallop, chunks of marine fish (not oily freshwater stuff).
• Good variety: silversides and similar whole marine feeders can be used sometimes, but do not make that the whole diet.
• Avoid: feeder goldfish/rosies (wrong fats), and huge meals that bloat them.

Feed smaller portions more often at first. Once they are established, 2-3 solid feedings a week is usually plenty for an adult, depending on size and tank temp. If the eel is always bulging and sitting out with a thick neck, you are probably overdoing it.

If it refuses food, do not panic on day one. Check the obvious: salinity swing, ammonia/nitrite, too much blasting flow over its chosen spot, or it does not feel secure. Sometimes just dimming the room and feeding after lights out gets you over the hump.

How they behave and who they get along with

Most of the time you will see a head sticking out of the sand and not much else. Then feeding time happens and suddenly it is a lightning strike. They are ambush predators, and anything that fits in their mouth is food, not a friend.

• Good tankmates: larger, confident fish that do not sleep on the sand and are not bite-sized (bigger tangs, larger angels, many midwater wrasses).
• Risky: bottom-sitters, sand sleepers, small gobies/blennies, small wrasses, and anything shrimp-sized if you want to keep clean-up crew intact.
• Inverts: expect losses. Snails may be ignored, but shrimp and small crabs are basically snacks.
• Other eels: I would not mix snake eels unless you have a very large system and a plan. Space and feeding competition can turn messy.

They are also diggers. That is not aggression, just lifestyle. If your rockwork is balancing on sand, it will eventually shift. Build like you expect tunneling, because you should.

Breeding tips

Breeding Moluccas snake eels in home aquariums is basically in the "has not really been done" category. Like many eels, they likely have a complicated life cycle with a larval stage that is not realistic to raise in a typical reef tank.

Common problems to watch for

• Escapes: the number one killer. Cover everything, and check your lid after maintenance.
• Starving in plain sight: a new eel may hide and not eat while you assume it is fine. Track feedings and body condition.
• Injury from rock shifts: unstable rockwork can crush an eel that is burrowed under it.
• Feeding accidents: striking at food can lead to mouth damage on sharp rock, or they can bite tankmates during a sloppy feeding.
• Water quality swings: they handle stable systems well, but they react badly to ammonia, nitrite, or big salinity changes.
• Parasites on arrival: watch for heavy breathing, flashing, or mucus. Quarantine is hard with burrowers, but observation tanks with sand trays can work.

One thing I learned the hard way: do not underestimate how much waste a messy eel feeding adds to the tank. If you feed chunky foods, you will see little bits get blown around. I like to shut off pumps for a minute, target feed, then siphon leftovers if anything gets away.