Opae Ula Shrimp (Halocaridina rubra): Ultimate Care Guide

Common Name(s)Opae Ula Shrimp, Tiny red shrimp, Volcano shrimp, Hawaiian red shrimp, Supershrimp, and Anchialine shrimp.
Scientific NameHalocaridina rubra
OriginVolcanic rock and Hawaiian Islands
Temperature70-80° F
Size1.5 centimeters
Minimum Tank SizeHalf a gallon
Food & DietAlgae
Lifespan20 years in captivity
Water pH8.0-8.5
Tank MatesBrackish-water tolerant species
Common DiseaseParasites, bacterial infections
Opae Ula
Opae Ula Shrimp (Halocaridina rubra)

Opae Ula Shrimp Facts

The Opae Ula shrimp are the perfect invertebrates for beginners to add to your fish tank. If you are considering adding an invertebrate to your community tank and are looking for an easy to care for species, then read on to find out more about this crustacean.

The Opae Ula shrimp is a very small shrimp that is known for its bright red coloration throughout its body. It is a common shrimp used throughout the aquarium hobby niche because it is a hardy and easy to care for species.

Other names you might hear the Opae Ula shrimp be called include volcano shrimp, anchialine shrimp, or Hawaiian red shrimp.

The natural habitat of the Opae Ula shrimp are the areas near the Hawaiian Islands. You can find them in tidal pools or anchialine pools. Anchialine comes from the Greek language and means “near the sea”.

An anchialine pool is inland and gets its water from under the surface near the ocean. This makes the water very brackish. In general, the Opae Ula shrimp can be found in moderately lit shallow pools or within dark crevices below the pools. These small crustaceans thrive in these types of waters because they have evolved to live in brackish-type waters.

The bright red color of these shrimp are eye-catching and complement any community tank scenery. An interesting fact is that when these shrimps are stressed they become translucent temporarily losing their red coloration. As the shrimp acclimates to its environment, you should see this phenomenon disappear and the bright red coloration come back.

You may be intrigued to know that these low maintenance pets do not require any special pumps, filters, lighting, etc. They thrive in tank conditions that match their natural habitat and can live for up to 20 years.

In their natural habitat, the Opae Ula are not endangered. There species are considered to be numerous, however their habitats such as certain tide pools are threatened due to rising sea waters that may be associated with climate change.

Opae Ula Shrimp Care

As a general rule, Opae Ula shrimp are easy to care for because they are quite hardy and can survive in a wide range of conditions.

Opae Ula shrimp are the easiest shrimp to own and require little maintenance. The important thing is to have the right tank for your shrimp. 

Size and Lifespan

The Opae Ula shrimp are tiny! These species of shrimp are small and measure up to 1.5 centimeters.

For their small sizes, they tend to have long lifespans. Under proper conditions, expect your Opae Ula shrimp to live as long as 20 years.

Opae Ula shrimp are peaceful and often slow moving. They are grazer feeders and primarily eat algae. 

Food and Diet

An interesting behavior you can observe from the Opae Ula shrimp is their feeding mechanism. They use both of their pair of claws (or technical term chelipeds) to rough up the substrate in a fast but purposeful manner.

The resulting cloud of particles makes up a large portion of the Opae Ula shrimp’s diet. They scrape and filter feed using their chelipeds. 

It is essential to build your tank so that the shrimp’s natural behaviors are encouraged. They are grazers and will feed on algae and biofilm that grows freely in the tank because of the natural behaviors of the shrimp. It is an interesting cycle to observe.

Opae Ula shrimp can feed on lightened vegetables or simple fish foods. Shrimp flakes are encouraged. Opae Ula almost always will naturally eat their required energy if there is a consistent amount of algae and biofilm.

Opae Ula shrimp will also consume algae “vines” that grow from the natural accumulation of algae and biofilm.

Tank Size and Setup

Any tank will work for the Opae Ula shrimp because they don’t need a lot of room to move and don’t require a filter. For example, you can start with a jar as your first tank to house your Opae Ula shrimp.

If you plan on housing a medium to large population of Opae Ula shrimp, you may wish to consider upgrading to a half-gallon or up to a five-gallon tank.

Here are some helpful guidelines when thinking about tank setup:

  • For the hardscape, use dark rocks or ocean rocks because you are trying to mimic the brackish pools found in Hawaii. Brackish means a mixture of salt and freshwater.  
  • Don’t introduce wood because it’s decomposition releases harmful chemicals for the Opa Ula shrimp
  • Light sand is a great substrate material and would have a nice contrast to dark lava rocks
  • A light would be a great option if the tank won’t be exposed to any natural light
  • Regularly check and maintain the tank every few weeks.

A great bonus for taking care of Opae Ula shrimp is that they do not require heavy maintenance and can be left alone. They don’t produce significant waste.

The best water conditions for Opae Ula shrimp is brackish water, which is a mixture of freshwater and saltwater. The water can be any temperature but the best range is between 70-80°F.

The optimal pH of the brackish water should be fairly acidic or at least 8.0-8.5.

A filter is not essential because the shrimp’s natural behaviors add to the biological filtration occurring in a well set-up tank.

In terms of salinity, Opae ula shrimp thrive the best when at least half of the water is saltwater, so they do have high salinity requirements. But they are hardy animals and can survive in levels far below that.

Keep in mind that these shrimp don’t do well in freshwater. It is also recommended to use marine salt to maintain consistent salinity levels. Do not use aquarium salt.

Opae Ula shrimp do not need plants in their tanks. The natural accumulation of algae and biofilm sometimes produces algae “vines”. These naturally occurring products grow and can be used as hiding spots or consumed as food.


How can you tell the difference between male and female Opae Ula shrimp? They are very tiny invertebrates, so it is difficult to distinguish between the two. The best way to know the sex of your shrimp is to use a microscope and observe the swimming limbs attached to the abdomens known as the pleopods.

The pleopods have subtle differences in their appearance between the male and female Opae Ula shrimp.

If you want to properly create the proper environment that best induces breeding behaviors then follow this quick checklist for your Opae Ula shrimp:

  • Make sure the water is warm (between 70-75°F)
  • The pH should hover around 8.0 to 8.4
  • Measure the specific gravity to 1.010 – 1.013 using a refractometer
  • Make sure your Opae Ula shrimp are sexually mature. This usually occurs after one year of age.
  • Make sure to have enough tank space (anything greater than half a gallon should work)

When the female is ready to molt, it releases hormones in the water which male Opae Ula shrimp can recognize. This signals the mating process to occur.

An interesting behavior found in female Opae Ula shrimp is that the female carries the eggs underneath the abdomen. This stage can be referred to as the “berried” stage.

Female Opae Ula shrimp can hold their eggs on the abdomen for up to a month before releasing larvae.


Although these species of shrimp are hardy, they are not immune to diseases and infections from bacteria or parasites.

Just keep an eye out for any strange behaviors or signs of discoloration on their bodies. Be sure to catch any breakouts early to avoid harming the total population.

Opae Ula shrimp are known to go translucent when frightened, so it is not abnormal to witness some translucency on several newly introduced shrimp as they adjust to their environment.

Best Tank Mates

The best tank mates for Opae Ula might be the Malaysian Trumpet Snails. The only options are other species that can tolerate the brackish water conditions that Opae Ula shrimp thrive in.

Where can I find Opa Ula for sale?

Online retailers and aquarium hobby stores will often have Opae Ula shrimp for sale, especially as food. Breeders of these and other kinds of shrimps or invertebrates may be available as well to be purchased for aquariums and tanks. 

Pricing varies typically on quantity of shrimp and can range from as little as $20 to $100 depending on the amount.

Opa Ula vs Cherry Shrimp

The Opae Ula shrimp and the cherry shrimp are two difference species but are similar in appearance.

The main difference is that the cherry shrimp is larger and requires different water conditions and tank requirements when compared to the Opae Ula shrimp.

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