Blache's ooze eel

Where they come from

Blache's ooze eels live way down on muddy continental slopes in the deep sea. Think cold, dark, and quiet. They spend most of their time buried in soft sediment with just the head out, waiting for something edible to drift by or crawl too close.

Setting up their tank

I kept one as a rescue in a dedicated coldwater system, and I'll be straight with you: this is not a living room fish. If you do try, build the tank around the eel, not the other way around.

• Big footprint tank: 180-240 gallons for one adult. Length matters more than height.
• Cold water: 4-8 C is the comfort zone. Mine did best around 6-7 C. You need a serious chiller.
• Salinity: 34-35 ppt, steady. No swings.
• Very high oxygen: cold water holds more O2, but they still like it brisk. Oversize your skimmer and keep good gas exchange.
• Low light: dim to dark. Use red viewing lights if you want to watch it at night.
• Escape-proof: tight lid with every gap sealed. Eels test lids. This one is relentless.

Give it something that feels like a mud burrow without actually putting muck in your display. I bury 1.5-2 inch PVC runs under 6-8 inches (15-20 cm) of fine sand. Cap some ends, leave a couple of discreet entrances. Weight and pin the pipe so it cannot float. Rockwork should be stable and set on the glass or egg crate before sand goes in.

Flow should be gentle, with a slow sweep along the bottom. Avoid blasting the substrate. I run heavy filtration on the sump and keep the display calmer so the eel can sit with its head out of the burrow without fighting current.

What to feed them

They are slow, opportunistic feeders. Mine ignored pellets and most live prey, but took soft marine meats once it settled. Feed sparingly; their metabolism is low at cold temps.

• Thin strips of squid or cuttlefish
• Soft pieces of marine fish (hake, pollock, silversides)
• Peeled shrimp or prawn, cut into fingers
• Clam or mussel meat (small portions)

How they behave and who they get along with

Picture a shy snake-head popping out of the sand, waiting. That is most of the show. They are not aggressive in the chase, but anything bite-sized that lingers by the burrow can vanish. They rearrange sand mouths and can undercut loose rocks.

• Best kept alone. Life is easier that way.
• If you must try tankmates: large, calm, coldwater fish that ignore the eel and can handle 6-8 C. Think temperate, not tropical.
• Skip crustaceans and small fish. They are snacks.
• Not reef-safe. Burrowing and low temps make corals a non-starter.

Breeding tips

Nothing practical to share here. Like other eels, they have a leptocephalus larval stage and deep-sea spawning is not something we can replicate at home. No captive breedings I am aware of. Plan for a single, long-lived display animal if it adapts.

Common problems to watch for

• Refusal to feed: Keep it dark, offer tiny pieces on tongs at night, and do not hover. Try squid first. Check that temperature is truly cold and stable.
• Barotrauma on arrival: Bloated body, odd buoyancy, bleeding from gills. Most do not recover. This is on collection, not you.
• Abrasions and secondary infections: Their skin is delicate. Use soft, fine sand and no sharp rocks. Treat infections in QT with coldwater-safe antibiotics if needed.
• Escape attempts: Any gap is a door. Double-check lids after every maintenance session.
• Chiller failure or big temp swings: They crash fast above ~10 C. Use a temperature alarm and redundant chilling if you are serious.
• Water quality swings: Deep burrows trap detritus. Siphon the surface lightly, do not stir the whole bed. Let the sump do the heavy lifting.