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Scientific name
Aplysia juliana
Family
Aplysiidae (Sea hares)
Adult size
4-8 inches
Min tank size
50 gallons
Temperature
74-82°F
Salinity
1.024-1.026
Temperament
Peaceful
Difficulty
Intermediate
Lifespan
1-2 years (short natural lifespan)

About the Yellow Sea Hare

Yellow sea hares are large herbivorous mollusks that specialize in eating hair algae - a single sea hare can clear a major outbreak in 2-3 weeks. Distinctive lemon-yellow body with parapodial flaps that pulse during movement. Short natural lifespan (1-2 years) and tendency to release toxic ink when stressed are the trade-offs. Use as targeted hair algae treatment, not permanent cleanup crew.

Native range: Indo-Pacific. Most US trade specimens come through marine wholesale suppliers in Indonesia, the Philippines, Hawaii, and the Caribbean. Wild collection remains the primary sourcing method for the majority of marine inverts - few are captive-bred at commercial scale. Quality of acclimation at the wholesale/retail stage is the biggest single predictor of long-term survival in home aquaria.

Tank setup and parameters

Tank size: 50 gallons. Parameters: temperature 74-82°F, salinity 1.024-1.026, plus the standard reef tank requirements - stable calcium 420-440 ppm, alkalinity 8-10 dKH, magnesium 1300-1400 ppm, nitrate under 25 ppm, phosphate under 0.05 ppm. The species requires conditions consistent with a healthy reef tank rather than nutrient-stripped sterile water - well-established systems with diverse microfauna and biofilm typically support these inverts better than newly-cycled tanks.

Lighting: depends on species. Photosynthetic inverts (clams, anemone-symbiotic species) require high-PAR reef LED lighting. Filter-feeders (worms, scallops) prefer moderate lighting and benefit from particulate-rich water. Flow: moderate, indirect flow works for most inverts - direct high-velocity flow stresses or damages soft-bodied species.

Acclimation: drip acclimate over 2-4 hours for hardy species, 4-8 hours for sensitive species (Linckia stars, sea hares, demanding nudibranchs). Never expose inverts to air during transfer - capture in a bowl underwater and transfer wet.

Diet and feeding

Yellow Sea Hare diet: Hair algae specialist - eats massive quantities. Feeding strategy depends on dietary type. Algae eaters require established tanks with biofilm and microalgae growth - new tanks lack the algal base they need. Carnivore inverts (starfish, some snails) need targeted meaty feedings 2-3x weekly. Filter feeders (clams, worms, scallops) need phytoplankton in the water column. Photosynthetic species need adequate lighting plus supplemental amino acid or coral food dosing.

Compatible tank mates

Safe: Reef community with covered powerheads.

Avoid: Tanks with exposed pump intakes; once hair algae is gone, they need to be moved.

Breeding

Captive breeding rare. Hermaphrodites - all individuals can reproduce.

Common problems and solutions

Pump intake death (most common - releases toxic ink); starvation after hair algae cleared; short natural lifespan.

Keeper note: NEVER expose to powerheads or pump intakes - the soft body can be sucked in and shredded, releasing toxic ink that crashes the tank. Cover all intakes with foam pre-filters. Remove sea hare from tank once hair algae is cleared (they will starve otherwise).

Frequently asked questions

How fast do sea hares clear hair algae?

A 4-inch sea hare can clear a 75-gallon tank of moderate hair algae in 2-3 weeks.

Are sea hares toxic to fish?

They release purple ink when stressed. The ink is mostly harmless but if a sea hare is shredded in a pump intake, the toxic release can crash water quality.

What happens after my hair algae is gone?

Sea hare starves. Plan to remove and trade/donate to another tank with hair algae, or accept that the sea hare won't survive long-term.

How much do sea hares cost?

$20-50 depending on size.

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