Spiny grenadier

Where they come from

Spiny grenadiers are deep-slope rattails from the outer continental shelf and upper bathyal zones. Think several hundred meters down, cold and dim, cruising over soft bottoms for worms and crustaceans. You will not see them on a reef. Most that show up in captivity are accidental bycatch.

Setting up their tank

Plan for a large, chilled, low-light system. They are long-bodied cruisers, not rock huggers, so give them room to glide and a soft bottom to probe.

• Tank size: 250+ gallons (950+ L) with at least a 6 ft (2 m) run. More is better.
• Temperature: 4-8 C. Hold it rock steady. Use a reliable chiller with 2x redundancy if you can.
• Lighting: very dim. Red spectrum works well for viewing without stressing them.
• Substrate: fine sand, 2-3 cm, kept very clean. Mud looks authentic but is a maintenance headache.
• Aquascape: open swimming lane with a few low, stable rock mounds. No sharp edges.
• Flow: gentle, broad flow along the bottom. High oxygenation without blasting them.
• Filtration: oversized skimmer, big biofilter, and lots of gas exchange. Cold water holds more O2, but they still like it high.
• Covers and intakes: tight lid and guarded overflows. Long tails find gaps and weirs.

What to feed them

They are benthic pickers and scavengers. Fresh, marine-based foods work best. Scent matters more than movement at these temps.

• Staples: chopped shrimp, squid, clam, mussel, lancefish, and krill.
• Smaller items: PE mysis or finely chopped clam to start new arrivals.
• Occasional: pieces of marine worm (if you can source safely) to trigger interest.
• Supplements: soak foods in a marine vitamin mix a couple times a week.

Feed on the bottom with tongs or a feeding stick, near their path. Small portions, 1-2 times a day at first. At 4-8 C their metabolism is slow, so once stable you can go to a modest daily feed or slightly heavier every other day. Pull leftovers within 10 minutes.

How they behave and who they get along with

Picture a quiet, methodical cruiser. Mine patrolled the bottom in slow laps, then paused to nose into the sand. They spook from fast movement and hate bright light, but they are not aggressive.

• Tankmates: best in a species setup or with other non-aggressive coldwater, deep-demersal fish that tolerate 4-8 C (think cusk-eels or snailfish in public aquaria).
• Avoid: crabs and shrimps (they may become food), boisterous swimmers, anything warmwater, and sharp décor.
• Group keeping: mixed results. They generally ignore each other, but space and food competition can stress weaker fish. If you try more than one, add them together and feed generously at multiple spots.

Breeding tips

Realistically, you can skip breeding plans. Spiny grenadiers are deep-sea spawners, likely releasing pelagic eggs far offshore. I am not aware of any home or public aquarium breedings. If you keep more than one, you might see size and seasonal changes in condition, but that is as far as it usually goes.

Common problems to watch for

• Heat spikes: the number one killer. Use temperature alarms and backup power for the chiller.
• Low oxygen: watch for faster gill movement and hanging near returns. Increase aeration immediately.
• Decompression/collection injuries: odd buoyancy, hemorrhages in fins, or listlessness on arrival. Dim light, perfect water, and time help more than meds.
• Refusal to eat: try softer foods (clam/squid), feed at night under red light, and reduce flow during feeding.
• Skin and snout abrasions: they rub glass and intakes. Round off rock edges and guard every opening.
• Medication sensitivity: go gentle. Many deep-sea fish react badly to strong copper or formalin. If you must treat, use a separate chilled QT and lower doses with heavy aeration.
• Internal issues from rich foods: at cold temps, overfeeding leads to regurgitation and fouled water. Keep portions small and consistent.