Vivaldi's catshark

Where they come from

Vivaldi's catshark is a deepwater Bythaelurus from the northwestern Indian Ocean, out on the continental slopes around the Gulf of Aden and nearby waters. Think cold, dark, and quiet. They cruise over soft bottoms hundreds of meters down, where the water barely changes season to season.

Setting up their tank

This is a cold, dim, high-oxygen setup. If you have not run a chilled marine system before, practice on something easier first.

• Tank size - prioritize footprint: at least 400-600 gallons with a 7-8 ft long x 3 ft wide footprint. Rounded corners or a pond-style oval are great for reducing snout scrapes.
• Temperature - 6-10 C, rock steady. Big chiller, insulated plumbing, and lids to reduce heat gain. Use a temp controller with alarms.
• Salinity and pH - 34-35 ppt, pH 8.0-8.3. Keep it boring and stable.
• Oxygen - high saturation. Oversized skimmer, strong surface agitation, and do not let the sump go stagnant. I run an O2 meter in cold shark systems.
• Lighting - very low. Ambient room light or a dim blue strip is enough. They are happier in the dark.
• Substrate - soft fine sand (2-5 cm). Avoid sharp rock piles. Build burrows and overhangs with PVC arches and smooth boulders.
• Flow - gentle laminar flow along the bottom so waste moves to overflows without blasting them. Return jets aimed above the substrate.
• Filtration - heavy. Big skimmer, lots of mechanical filtration you can rinse every few days, and a UV sterilizer helps with the bioload.
• Covers - tight lids and screened overflows. Sharks explore. Keep cords and intakes guarded.

Acclimation matters. Drip over 60-90 minutes in a dark tub with active aeration and temperature control. Transfer with a soft sling, never by the tail.

What to feed them

They take meaty marine foods, but many are shy at first. Evening feedings in low light work best. I use tongs and place food just ahead of the snout so they can find it by scent.

• Starter options - squid strips, raw prawn, clam, and silverside pieces usually get interest first.
• Rotation - mix in pieces of marine fish (hake, pollock), scallop, mussel. Avoid making thiaminase-heavy fish (like smelt) the sole diet.
• Supplements - soak foods 1-2x weekly with a marine vitamin mix and iodine to cover gaps.
• Portions - small but frequent. Juveniles: every 2-3 days. Adults: 3-4 small meals per week. You want a steady body condition, not a bulging belly.
• Clean-up - remove leftovers within 10 minutes. Cold systems hide decay, but it still nukes water quality.

How they behave and who they get along with

Think quiet and methodical. They hug the bottom, rest under cover most of the day, and get moving at night. Not bullies, but anything bite-sized is food.

• Best setup - species-only. Life is easier for everyone.
• If you must mix - only with other coldwater, non-nippy species too large to swallow and not prone to grabbing fins. No triggers, puffers, or pickers.
• Multiple sharks - only in very large footprints. Provide multiple hides and sight breaks. Watch for fin-nipping and give them space.
• Handling - avoid. Their skin is like sandpaper and their teeth are no joke. Use a soft barrier or tub if you must move one.

Breeding tips

They are oviparous. You may see pairs of egg cases tucked under an overhang once they settle and body condition is steady. Breeding this species is rare in private tanks, but the general catshark approach applies.

• Sexing - males have claspers; females do not. Mature females are broader through the abdomen when cycling.
• Spawning cues - very stable cool temps, low light, and a quiet tank. Provide attachment points: coarse plastic mesh sheets or fake kelp tied to a rock.
• Incubation - at 7-9 C, expect a long wait (many months). Keep eggs in gentle flow with plenty of oxygen. Candle with a dim light to check development.
• Fungus control - flow across the case matters more than chemicals. If an egg fouls, remove it so it does not spread.
• Hatchlings - use a nursery pen with the same coldwater parameters. Start with small, soft seafood bits and frequent tiny feeds. Keep waste moving out.

Common problems to watch for

• Heat creep - pumps and room heat will push temps up. Insulate lines, vent your stand, and size the chiller generously.
• Low oxygen - cold water masks gas issues. Use an O2 meter if you can. Boost aeration during feeding and after maintenance.
• Snout and fin abrasions - from rough rock or tight turns. Smooth the scape and give them room. Treat secondary infections promptly in a hospital tank.
• Refusal to eat - new arrivals often sulk. Try squid first, feed at night, and cut the lights. Check for parasites if it persists.
• Shipping stress and barotrauma - deepwater fish arrive exhausted. Keep acclimation dark and calm. Watch for odd buoyancy or rolling.
• Copper or harsh meds - elasmobranchs do not tolerate them. Use shark-safe treatments and lots of aeration.
• Water quality drift - even small ammonia or nitrite shows up fast on sharks. Test often, rinse mechanical filters, and keep nitrates modest.