Arabian spiny eel

Where they come from

Notacanthus indicus is one of those deepwater oddballs that looks like an eel but is really a spiny eel (not the freshwater spiny eels people usually think of). They show up in the Indian Ocean region, typically along deeper slopes and soft bottoms. That deep, dim habitat explains a lot: they like it calm, they startle easily, and they are built for cruising near the bottom and picking off small prey.

Setting up their tank

This is an expert fish because the setup is unforgiving. They do best in a big, stable, low-drama marine system with excellent oxygenation and very clean water. Think more along the lines of a cold-to-cool deepwater display than a warm reef tank full of chaos.

• Tank size: bigger is better. I would not bother under 180 gallons, and a 6+ foot footprint makes life easier.
• Aquascape: open bottom space with a few low rock piles. Give them lanes to cruise, not a rock maze.
• Substrate: fine sand is your friend. They spend time on and in it, and coarse crushed coral can beat them up.
• Hiding spots: PVC elbows hidden behind rock work work great. Dark, snug retreats reduce panic.
• Flow: moderate, not blasting. You want good turnover and oxygen, but avoid a sandstorm.
• Lighting: keep it subdued. If you run bright lights, add shaded areas and let them have a dark corner.

Temperature is where a lot of people get tripped up. Many deepwater notacanthids do poorly long term in warm, tropical temps. If you cannot provide cooler water (and keep it stable), I would skip this species. If you can, you will usually see better appetite and less mysterious decline.

What to feed them

They are carnivores that want meaty, sinky foods. In my experience, getting them to recognize food is the make-or-break moment. Once they are eating confidently, they are still not a "throw pellets and forget" fish.

• Best starters: live blackworms (if you have a clean source), enriched live brine as a teaser (not a staple), small live shrimp
• Go-to frozen: mysis, chopped raw shrimp, chopped clam, squid strips, quality marine carnivore blends
• Prepared: some will take sinking carnivore pellets eventually, but I would not count on it early

Small, frequent meals beat one huge dump of food. They are deepwater hunters, not surface piggies. If you blast the tank with food, you just spike nutrients and the eel gets outcompeted.

How they behave and who they get along with

Arabian spiny eels are generally calm and a bit spooky. They are not looking for fights, but they will eat what they can fit in their mouth. Most of the "compatibility" problems are actually feeding problems: fast fish steal everything, and the eel slowly wastes away.

• Good tankmates: peaceful, slower midwater fish that will not mob food (think deepwater/temperate-leaning community choices if your temp matches)
• Avoid: aggressive triggers, big wrasses that hunt the bottom, puffers that nip, anything that will harass a shy fish
• Also avoid: tiny fish and shrimp you are emotionally attached to

Breeding tips

Realistically, breeding this species in home aquariums is not a thing at the moment. Deepwater spawners often have specific cues (seasonal changes, pressure, temperature shifts, long-distance migrations) that we cannot reproduce. If you keep one alive long term and feeding well, you are already doing something most people cannot pull off.

Common problems to watch for

Most losses come from a slow slide: the fish hides, eats poorly, and fades over weeks. You want to catch issues early, because once they are skinny it is hard to bring them back.

• Refusing food: often stress, too much light, too much activity, or temperature too warm
• Being outcompeted at feeding time: the eel looks "fine" but never gets its share
• Skin damage and infections: scrapes from rockwork can turn into bacterial issues fast in a stressed fish
• Parasites from wild collection: flukes and internal parasites are common suspects if appetite is weird or weight drops
• Oxygen issues: heavy breathing and hanging in high-flow areas can mean low O2, especially in warmer water

My biggest practical tip: set a routine and stick to it. Same feeding zone, same dim period, minimal hands-in-tank chaos. These deepwater fish settle in when the tank feels predictable, and that is usually when they finally start eating like they mean it.