Nebulous snake eel

Where they come from

The nebulous snake eel (Xestochilus nebulosus) is one of those secretive Indo-Pacific reef and rubble-zone eels that spends most of its life buried with just its head poking out. In the wild you find them around sandy patches near rock and coral rubble, especially where there are lots of little crustaceans and small fish to ambush.

That wild lifestyle explains basically everything about keeping them: they want to hide, they want to dig, and they will take off through any gap you forgot about.

Setting up their tank

Think "secure sand burrow with a bolt-hole" more than "pretty open reef display." If you give them the right bottom and cover, they settle in and you actually see them. If you do not, you get a stressed eel that either refuses food or goes walkabout.

• Tank size: bigger is better, but I would not do one in anything under 75 gallons. 120+ gallons makes life easier because you can build a wider sand area and keep tankmates that will not bother it.
• Sand bed: 3-6 inches of fine sand. They like to bury. Coarse gravel can scrape them up and they will avoid it.
• Rockwork: stable and sitting on the glass or on a support grid, not perched on sand. They dig and can undermine rocks.
• Hiding options: a couple of PVC elbows or short lengths of pipe buried under/behind rock. They will use it like a den entrance.
• Flow: moderate is fine, but try not to blast the exact spot they want to bury in.
• Filtration: they are messy eaters, so plan for a strong skimmer and decent mechanical filtration you can rinse often.

Water parameters are standard reef range, but stability matters more than chasing a specific number. Big salinity swings and neglected nitrate creep show up as poor feeding response and skin issues pretty fast with these guys.

What to feed them

They are carnivores and very much "sniff and strike" feeders. Mine did best once it learned that food shows up at the same spot, around the same time. Expect a shy start, then a very enthusiastic eater once it clicks.

• Best staples: chunks of shrimp, squid, clam, mussel, scallop, and marine fish flesh (not freshwater feeder fish).
• Good variety: silversides or similar marine whole fish occasionally, and enriched frozen foods if they will take them.
• Avoid: relying on krill as the main food (can be fatty and messy) and anything with thiaminase-heavy feeder habits long term.
• How often: adults 2-3 times per week is usually plenty. Juveniles can take smaller meals more often.

If a new eel refuses food, dim the lights, reduce activity around the tank, and try scentier options like clam or fresh shrimp. Sometimes letting the food sit near the burrow for a minute helps. Just siphon leftovers quickly so you do not foul the sand bed.

How they behave and who they get along with

Most of the time you will see a head poking out of the sand, watching the room like a little periscope. At night they get bolder and may cruise along the bottom. They are not a "pet eel that swims around all day" type.

The big rule with tankmates is simple: if it can fit in the eel's mouth, it is food. If it harasses the eel or steals every bite, the eel loses.

• Good tankmates: medium-to-large peaceful fish that stay in the water column (tangs, larger wrasses that are not hunters of burrowers, rabbitfish, many angels with caution).
• Use caution: triggerfish, puffers, large hawkfish, aggressive wrasses, and anything that likes picking at faces. They can stress or injure the eel.
• Not safe: small gobies, small blennies, tiny wrasses, ornamental shrimp, and crabs you care about. Snails are usually ignored, but hungry eels do weird things.
• Other eels: possible in big tanks with lots of space, but mixing eels is always a gamble. I would not try it unless you can separate them if it goes sideways.

Breeding tips

Realistically, breeding nebulous snake eels in a home aquarium is not something you should plan around. Like many marine eels, they have a complex larval stage (leptocephalus) that is not currently being raised by hobbyists in typical setups.

If you ever see two individuals doing looping, synchronized swimming at dusk and then disappearing, that can be spawning behavior in some eel species. It is still a neat observation, but do not expect babies to show up and grow out in your tank.

Common problems to watch for

• Not eating: usually stress (too bright, no secure burrow, too much competition at feeding time) or a fresh import that needs time. Try quieter conditions and tong feeding.
• Jumping/escaping: almost always a lid or overflow issue. Fix the top before you buy the eel, not after.
• Skin scrapes and infections: rough substrate, unstable rock that collapses, or forcing the eel out of hiding. Keep sand fine, rock stable, and let it settle in.
• Ich/velvet sensitivity: eels do not handle harsh treatments the way many fish do. Quarantine is smart, but research eel-safe methods and avoid copper without knowing exactly what you are doing.
• Poor water quality from messy feeding: big chunks of food get lost in the sand. Feed at the burrow, remove leftovers, and keep up with mechanical filter cleaning.

If you can give them deep fine sand, a secure lid, and calm feeding sessions, they are surprisingly hardy. The "advanced" part is mostly about setup discipline and resisting the urge to keep them with snack-sized tankmates.