Rattail (grenadier)

Where they come from

Grenadiers (rattails) like Ventrifossa rhipidodorsalis are deepwater fish. Think cold, dark slopes and basins where the pressure is high and food shows up in small, meaty bursts. You are basically trying to keep a creature that evolved to live way below the reefs most of us are used to.

Setting up their tank

This is an expert fish because the tank is the hard part, not because it is aggressive or picky in the cute way. They come from cold, stable water. A typical 78F reef tank is basically a fever.

If you are serious, plan on a chilled marine system. I would treat 45-55F as the neighborhood you should be aiming for, with very small swings day to day. Stability matters more than chasing a magic number.

• Tank size: bigger than you think. I would not bother under 180 gallons, and 300+ is much more forgiving.
• Temperature: chilled system (roughly 45-55F). Use a real aquarium chiller sized for the full system volume, not wishful thinking.
• Lighting: dim. These fish do not need bright lights, and bright tanks tend to stress them.
• Flow: moderate and smooth. Avoid blasting them with powerheads like you would in an SPS tank.
• Aquascape: open bottom area plus a few shaded caves/overhangs. They like a place to sit and feel hidden.
• Filtration: heavy biological capacity and aggressive export. Big skimmer works well even in cold systems, plus mechanical filtration you actually clean.

Use a tight lid. Rattails are not famous jumpers like wrasses, but stressed deepwater fish can do odd things at night, and you do not want to learn the hard way.

What to feed them

They are meat eaters, and they tend to feed off the bottom or just above it. The trick is getting food to them without every faster fish in the tank stealing it first.

• Start with: thawed mysis, chopped krill, chopped clam, shrimp pieces, squid strips
• Great staples once eating: mixed frozen "marine carnivore" blends, chopped fish flesh (sparingly), roe/eggs for variety
• If they are hesitant: try live blackworms (if you can source safely), live ghost shrimp, or very fresh chopped seafood to kick-start feeding

I have had the best luck feeding after lights-out or under very dim lighting. Use tongs or a feeding stick and place food right in their zone. Once they learn the routine, they get bolder, but they are rarely "race to the surface" fish.

How they behave and who they get along with

Expect a calm, low-energy fish that spends a lot of time hovering or resting near the bottom. They are not a showy "always swimming" species. The cool part is their weird deepwater vibe, not constant activity.

Tankmates are mostly about temperature and speed. Anything that likes normal tropical temps is out. Anything fast and food-crazy will outcompete them. Anything that can fit in their mouth is a snack.

• Good neighbors: other coldwater, non-aggressive deepwater species that eat similar foods and are not hyper-competitive
• Avoid: triggers, puffers, aggressive groupers, big predatory eels, and anything that will harass slow fish
• Also avoid: tiny fish and small shrimp/crabs you want to keep long-term (they may disappear)

Breeding tips

Realistically, breeding Ventrifossa rhipidodorsalis in home aquariums is not a thing right now. Deepwater rattails have complex life histories, and even sexing them can be guessy without imaging or dissection.

If you ever end up with a pair (or a group) that settles in long-term, the best "breeding tip" I can give is to keep the environment boring: cold, stable, low light, consistent feeding, and no bullying. Longevity is step one, and it is already the hardest step.

Common problems to watch for

• Heat stress: rapid breathing, lethargy, refusing food, hanging in high-flow or near returns looking for oxygen
• Buoyancy issues from collection/shipping: floating, rolling, inability to stay down, abnormal posture
• Starvation by competition: the fish looks "fine" but slowly gets thinner because tankmates eat everything first
• Mouth and snout injuries: from hitting glass during stress or shipping, can lead to infections
• Cold-system water quality complacency: cold water can mask problems until they suddenly show up

Quarantine helps, but be realistic: matching temperature in QT is the big hurdle. A warm QT followed by moving to a cold display is stressful, and the reverse is not great either. If you do QT, set it up as a true cold QT with hiding spots and gentle flow, and focus on getting it eating confidently before you do anything else.