Nudibranch (sea slug)

Starvation / wasting

SignsBody shrinks day by day, color fades, rhinophores stay retracted, curls up on the bottom, food is not being eaten

PreventionIdentify the food organism before collecting and take the animal together with its food. Do not collect species whose food cannot be secured; return them to the sea early

Ammonia poisoning

SignsSuddenly falls off the glass, produces lots of mucus, body surface turns white and swollen, no movement

PreventionTest ammonia and nitrite daily and keep both at zero. Small, frequent water changes. Remove uneaten food and dead matter immediately

Osmotic shock

SignsBody swells or shrinks right after a water change or top-up, gills collapse, dissolves the next day

PreventionCheck specific gravity 1.023–1.025 daily. Top up evaporation with fresh water in small amounts. Water changes at the same temperature and specific gravity

Heat stress

SignsStops moving in summer, gills and projections shrink, body surface peels, dissolves within days

PreventionKeep the water temperature of the collection site (temperate species about 15–22°C). A cooling fan or chiller is essential in summer

Body-surface breakdown (melting)

SignsPart of the body turns cloudy white and dissolves, projections fall off one after another, foul smell, strands of mucus

PreventionTriggered by injury and poor water quality. Do not touch with nets or tweezers. Isolate melting individuals to protect the main tank

Parasitic copepods

SignsWhite thread- or sac-like objects (parasite egg sacs) on the back, body becomes thin

PreventionInspect the body surface closely when collecting and do not take parasitized individuals. Do not try to remove them; pulling tears the body

Sucked into the pump

PreventionCover intakes and pump inlets with sponge. Keep flow weak. Intakes near the surface are especially dangerous

First aidTurn off the power, take the pump apart underwater and free the animal gently. Do not pull on the body. Leave torn individuals to rest in a separate container

Tears from nets or tools

PreventionDo not grab with nets or tweezers. Move by scooping it up in a container underwater or letting it crawl onto a card

First aidDo not touch it further. Leave it to rest in a separate container of clean seawater with no flow. Isolate if it starts to melt

Predation by tankmates

PreventionDo not house with crabs, hermit crabs, wrasses, etc. Keep alone or with the same species only, in a small container

First aidMove the attacker to another container immediately. Leave the injured animal to rest and watch where gills or projections were lost

Drying out / exposure to air

PreventionIf it climbs above the waterline, adjust the water level. During transport, fill the container with seawater so it never touches air

First aidReturn it to seawater. A dried, shrunken animal may be protecting itself with mucus; do not touch it and wait for recovery

Vibrio wound infection

RouteBacteria enter through cuts on the hands from seawater or rocks

PreventionDo not put hands with cuts into seawater. Wear gloves and wash with soap afterward. People with liver disease must be especially careful

Fish-tank granuloma

RouteNontuberculous mycobacteria enter through cuts on the hands

PreventionWear gloves for tank work. If a red, slow-healing swelling appears on your hand, see a dermatologist and mention your aquarium work

Dermatitis from stinging cells

RouteTouching the stinging cells stored by aeolid nudibranchs with bare hands

PreventionNever touch aeolid nudibranchs bare-handed. If stung, rinse with seawater, do not rub, and cool. See a doctor if swelling spreads

Poisoning from defensive chemicals

RouteTouching eyes or mouth with hands that handled a toxic individual

PreventionAfter touching, wash hands and do not touch eyes or mouth. Keep out of reach of small children and pets. If swallowed, seek medical care

Food

• Food is species-specific. Hypselodoris festiva eats particular sponges; aeolids eat hydroids, etc.
• Collect the food organism at the same site. Bringing home an animal together with the food it is sitting on is the only method
• Species whose food cannot be secured cannot be kept. Return them to the collection site before they starve

Water

• Natural seawater from the collection site or artificial seawater. Specific gravity 1.023–1.025, temperature the same as the collection site
• Ammonia and nitrite must be zero. Change 1/4 of the water 1–2 times a week at the same temperature and specific gravity

Toys & play

• No toys needed. The food organism itself is its living space
• Live rock and uneven rock give it surfaces to crawl on and hide in
• Strong lighting is unnecessary. Dim light that does not harm the sponge or other food is enough

Nest, bed & hideout

• It rests on its food or in the shade of rocks
• Provide quiet rock crevices out of the current

Bedding & litter

• No substrate, or a thin layer of coral sand. A thick bed becomes a source of decay
• Place rocks and sponge-covered stones from the collection site
• Remove feces and mucus daily with a pipette

Cage / housing material

Small glass or clear plastic tank. Gap-free lid, sponge on the intake

Size & space

About 10–30 L. Larger volumes are more stable, but the animal may lose track of its food

Layout

• Place the pump and intake near the bottom and cover with sponge
• Put the food organism in the center so the animal can reach it quickly
• Run a weak current along the walls. Never aim flow directly at the animal

Placement notes

• A spot away from direct sun and heater drafts where the water temperature stays stable
• In summer, somewhere a cooling fan or chiller can be installed

Exercise, free-roam & walks

• No walks. Let it move on its own across its food
• Do not take it out of the tank. Observe through the glass
• It can crawl out through gaps in the lid and fall, so check daily

Temperature & humidity

TemperatureSame as the collection site. Temperate species about 15–22°C, tropical species 24–26°C

HumidityHumidity is irrelevant. Replace evaporation with fresh water in small amounts

Summer & winter

• Summer: prevent temperature rise with a cooling fan or chiller. Keep ice packs ready for power outages
• Winter: temperate species often need no heater. Avoid sudden temperature changes

Nail trimming

No nails. Instead, make daily measurement and logging of specific gravity, temperature and ammonia your routine

Brushing, skin & coat care

Any care that touches the body is strictly forbidden. Siphon out feces and mucus with a pipette and remove food debris and decaying matter

Other care

Rinse equipment with fresh water; never use detergent. If an egg mass is laid, leave it and observe

Protection from predators

• Do not house with predators such as crabs, hermit crabs or wrasses
• Secure the lid so cats and small children cannot reach into the tank
• Keep the lid on to block mosquitoes and insects; never use insecticide in the room

Foreign-body ingestion

If a small child or pet puts a nudibranch in its mouth, the toxins and stinging cells are dangerous. Keep the tank out of reach. If swallowed, rinse the mouth and seek medical care

Being stepped on

Do not step on nudibranchs underfoot when collecting on the shore. Check the floor before walking so you do not step on one that fell out of the tank

Getting pinched

It can be torn when caught between the heater, rock and glass, or the edge of the lid. Secure rocks and leave no gaps

Falls

It climbs the glass, crosses the waterline and falls. Keep the water level 5 cm or more below the rim and the lid gap-free. If it falls, collect it with a container wetted with seawater

Escape

It can be washed into overflow pipes or filters. Cover every opening near the surface with sponge and count the animals every morning

Safe release procedure

1. Put on gloves and sink a container of seawater next to the animal
2. Place a thin plastic sheet or card in its path and let it crawl on by itself
3. Lift the container out underwater so the animal never touches air
4. Keep hands that touched it away from eyes and mouth and wash with soap

After the release

If stung, rinse with seawater and cool. See a dermatologist if swelling, numbness or hives spread

What to tell the vet & what to bring

Few clinics see invertebrates. Record a photo for species ID, collection site, temperature, specific gravity, food and days elapsed, and consult

Checking consciousness, breathing & heartbeat

• Alive if rhinophores and gills are open and contract when stimulated
• Normally it clings to the glass or its food and moves
• Melting, foul smell or body collapse means dead or dying

Stopping bleeding

• It has no blood. Do not touch tears; leave it to rest
• Move it to a separate container of clean seawater with no flow
• Isolate it from the main tank if it starts to melt

Transport

• Fill a sealed container completely with seawater so it never touches air
• Keep the collection-site temperature with ice packs; carry it dark and without shaking