Opae ula (Halocaridina rubra) care guide

Group

Shrimp

Other names

ʻŌpaeʻula, Hawaiian red shrimp, Volcano shrimp, Hawaiian supershrimp

Family

Atyidae

Origin

Endemic to the Hawaiian Islands, in brackish anchialine pools near the coast

Water

brackish

Maximum size

1.5 cm

Temperature

18–28°C

pH

7.5–8.5

Hardness

SG 1.005–1.020 (low brackish)

Minimum tank

4 litres

Care level

beginner

Temperament

peaceful

Lifespan

10+ (reported) years

Care

ʻŌpaeʻula is a tiny red shrimp, rarely over 1.5 cm, found only in the Hawaiian Islands, where it is the state shrimp. It lives in anchialine pools, which are brackish pools near the shore linked to the sea through porous lava or limestone, and in coastal caves and wells. It is usually red but can look yellow or orange. NatureServe lists it as Vulnerable. It is best known in the hobby from small sealed or semi-sealed glass ecosystems. Set-up: a small, stable tank or jar with rock, coral rubble or lava rock and good light to grow a film of algae suits a group. They need very little feeding and do best when left alone. Wikipedia gives no care figures, so the water figures here are general hobby guidance rather than from a source: low brackish water (roughly SG 1.005–1.020), 18–28 °C, and hard, alkaline water. Top up evaporation with fresh dechlorinated or RO water, never salt water, so the salinity stays steady. Behaviour and role: peaceful grazers that scrape algal and bacterial films from rocks, and can also filter-feed when the water turns green with phytoplankton. They moult now and then and leave silvery shed skins on the floor, which is normal. Colour often deepens in established tanks. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never treat a tank holding them with copper, check the label of any fertiliser or medicine, and keep nets and buckets used for copper-treated tanks separate. Sources: Wikipedia (en.wikipedia.org/wiki/Halocaridinarubra). Checked October 2026.

Diet

Herbivore and detritus eater. It scrapes the film of algae and bacteria off rock and also filter-feeds when phytoplankton is present. In a well-lit, mature tank it may need almost no extra food; give a pinch of spirulina powder or a crumb of algae wafer every week or two at most. Overfeeding is the most common cause of losses in small set-ups.

Breeding

In the wild they breed in the underground parts of their habitat. In aquariums breeding is slow and patchy; the larvae are tiny and need stable brackish water. Captive-bred stock is available, and buyers should choose captive-bred rather than wild-collected shrimp.

Compatibility and tank mates

Best kept on their own. Their brackish water and tiny size rule out most tankmates, and almost any fish will eat them. In the wild they are preyed on by a slightly larger shrimp, Metabetaeus lohena. Small nerite snails that tolerate brackish water can share their tank.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.