Opae Ula Shrimp – Detailed Guide: Care, Diet, and Breeding

Opae Ula is a kind of red-colored shrimp that lives in brackish water and is native to the Hawaiian islands. Do you know that the Opae ula species is known as “Halocaridina Rubra?” This shrimp has a bright red color, and that is why it has been given the name of “Opae Ula,” a Hawaiian phrase meaning “red shrimp.” 

An interesting fact about this shrimp species is that it can live for an extended period of 20 days! They are very resilient and hardy, so you can easily take care of these tiny creatures.

You will be surprised to know that this red shrimp doesn’t need any kind of filters, pumps, or food. Such a low-maintenance pet, you see? 

If you are an Opae ula shrimp owner, get delighted because you won’t have to take many pains. But, you need to take care of their diets and breeding. 

We have come up with this super informative guide to help you take care of your tiny red shrimps. We have a lot to unpack! So, let’s dive into the details now!

Origins, Natural Habitat Of The Opae Ula Shrimp

The Opae Ula shrimps have their origins at Maui, one of the Hawaiian islands and are mainly found in the brackish water of the ponds. They are so hardy that they can even thrive in extreme conditions of low oxygen levels, low-temperature conditions of -1 degrees Celsius. They can survive perfectly even without having any food for months. 

Opae ula shrimp

These red shrimps are also found in the tidal and Anchialine pools of Hawaii. Wondering what Anchialine pools are? The word has been taken from the Greek word “Anchialos,” which means “near the sea.”

These are inland water bodies connected with the ocean under the surface and are subjected to tidal flux, thus bearing a brackish nature. 

The two main natural habitats where the red shrimps are predominantly found are shallow ponds and dark crevices in the water table below those pools. 

Do you know that the sturdy nature of this shrimp has made it a perfect fish to be a part of ecospheres? These imply completely enclosed jars with no filtration or food, and the shrimps are made to live here for months.

Surprisingly, they can exist perfectly under these harsh circumstances. This Hawaiian red shrimp is growing highly popular among hobbyists owing to its praiseworthy resilience. 

Description Of The Opae Ula Shrimp

The Opae Ula shrimps are very tiny and grow to only half an inch, that is, 1.5 centimeters in length. They are available in a diverse range of vibrant colors such as yellow, orange, and light pink. However, bright red is the most common color in which the shrimp Halocaridina Rubra fish is found. 

The rich red color of the shrimp is so vivid and vibrant that the color of the water also changes to red when the shrimps go swimming under the pool collectively or in schools.

Interestingly, this red creature is that if it feels disturbed, it immediately loses its red color and turns pale for some time. After a few minutes or hours, its bright red color gets restored to its body. 

Molting Opae Ula Shrimp

It is not really known if this red shrimp performs molting or sheds its outer skin. The Opae Ula’s tiny body size, along with its slow rate of metabolism, rules out any chance of undergoing the molting process. 

Sexing Opae Ula Shrimp

Usually, in most Caridean shrimps, the males and females are easily distinguished by observing the features on the first and second pleopods. However, the Halocaridina Rubra shrimp has such a small body size that it is determined between males and females by placing it under a microscope. 

There is a skinny line of difference between the male and female pleopods or the limbs used for swimming. You can spot these on both the exoskeletons and the live shrimp. 

But, not everyone owns a microscope or is well-aware of the sophisticated scientific methods of sexing your pet red shrimp. In such a case, how can the volcano shrimp be classified as male or female? Let’s have a look at the specific features of the shrimp that are indicative of its sex. 

Adult females have broader abdomens to facilitate the carrying of eggs. On the other hand, the males have slimmer abdomens, and their undersides are pretty straight.

Besides, the female Hawaiian shrimp has a brighter, more vibrant red color than a male anchialine shrimp. Just a look at the saddle and clutch of eggs will quickly tell you the sex of this shrimp. 

The Feeding Styles of the Opae Ula Shrimp

Let’s look at the style that the opae ula follows at the time of consuming foods. 


The shrimps use this eating style by applying both pairs of chelipeds. While doing so, they keep their palms facing the downward direction to the substrate of the aquarium. Then, they lift their palms and reapply in fast succession. 

Filter Feeding 

This is another method by which the Opae Ula shrimp hold its chelipeds so that the fans of setae are kept exposed, and then these are positioned anteriorly. When it swims through the water in the tank, the fans filter out the small particles from the tank or pools water. 

opae ula

This mode of feeding is most fervently used by stream-dwelling shrimp such as Vampire shrimp and Bamboo Shrimp. The only difference in their habit is that the fans stay oriented to the water current and their bodies remain stationary. 

Usually, the Hawaiian shrimp prefer the first scraping method while feeding on algae, bacteria, diatoms, etc. They use the style of filter-feeding only in pool waters, where the phytoplanktons are available in large numbers. 

Feeding Opae Ula Shrimp

While dwelling in a tank, this anchialine shrimp will prefer to eat algae and biofilm. But, you may also feed these little red creatures fish food, flakes of shrimp, and slightly blanched veggies. Make sure to include in its diet the supplement of Spirulina. 

The best part about the maintenance and feeding of the red shrimp is that if you keep the fish tank under indirect sunlight, you have to feed it only after 2 to 3 weeks or one month.

This is because algae and biofilm form naturally on the water’s surface, as sunlight will be available in abundance. This shrimp also loves to feed on small insects that float at the water surface. 

If the shrimp don’t get access to algae, you can feed them shrimp pellets every one week or one month as an alternative to algae. 

Ensure not to feed the shrimp after one month or two because they will have access to algae, biofilms, and bacteria during that period, leading to overfeeding. Algae alone are enough to give the proper shrimp nutrition, and they can survive perfectly without facing any trouble. 

What Happens If You Overfeed Opae Ula Shrimp?

As an Opae Ula shrimp owner, you always need to remember that underfeeding it is still better than overfeeding it.

Even if you go on a trip and there is no one to feed the shrimp at home, it is alright. It can go without food even for two months, as it will continue to have algae from the water surface. 

If you have a 5 to 10-gallon tank with hundreds of red shrimp living inside, you will need only a single, tiny pellet to feed all of them. And, guess what? This single pellet will be adequate to provide all of them with nutrition. 

Since Opae Ula has a slow metabolism, it doesn’t feel the need to eat much. To ensure that a healthy environment is maintained inside the tank, remove the bits and pieces of uneaten food to prevent the water system in the tank from getting polluted. 

Mating Opae Ula Shrimp

Let’s look at the conditions to be fulfilled to make the mating of opae ula shrimp successful. 

  • Mating can be done only after the opae ula has reached the stage of sexual maturity, which is attained almost one year after hatching. Since the red shrimp are sold off when they are still juveniles, you need to wait for about 3 to 8 months after introducing them to the tank. 
  • Specific water conditions are to be present in the aquarium to make mating possible. To support breeding, the water pH has to be between 8.0 to 8.4. The levels of nitrates and ammonia in the water need to be at zero. The tank has to be a large one as much space has to be given to the shrimp for breeding. 

Make sure that the water temperature stays warm and in the range of 21 to 24 degrees Celsius. It must not be too salty. The salinity levels can be kept between 1.010 to 1.013 specific gravity. 

  • Create some dark, hidden structures in the tank so that the male and female shrimp can mate with each other. Once the adult female red shrimp discharges pheromones, the male shrimp get alerted. This marks the beginning of the mating process.  

Breeding Opae Ula Shrimp

Unlike Caridina shrimp, the Opae Ula shrimp tend to breed less often. The female shrimp possess the ability to breed only a few times a year. After the fertilization process is over, the females bear the eggs on their abdomens, and this phase is known as “berried.” 

The mature female red shrimp carry about 14 to 18 eggs in their bellies in total, each measuring approximately 1 mm for almost 27 to 38 days.

The larvae are released over 1 to 5 days, and these float at the tank’s surface. The yolk sacs pass through 4 zoeal stages and one mysis stage before final settlement. 

Do note that you won’t have to feed the larvae at all. Once the larvae cross the last stage of development known as megalopa, they reach their juvenile stage, and that is when they can be easily distinguished from the adult red shrimps in terms of their body sizes. 

Opae Ula Shrimp and Suitable Tankmates

Opae Ula Shrimp-Fish Compatibility 

It is not a good idea at all to keep the opae ula shrimp with fish. A majority of the fishes will feed upon the red shrimp if kept in the same tank. If the number of predators in the tank increases, the red shrimp of Hawaii will become inactive. They will try to hide out of the fear of being eaten by the fishes. That is why fishes are not at all compatible with red shrimp. 

Opae Ula Shrimp-Hermit Crab Compatibility 

The Hawaii dwarf hermit crabs are highly compatible with opae ula shrimp. These crabs have a size of less than 1 inch, and they won’t bother the shrimp. So, you can consider keeping them together. 

Opae Ula Shrimp-Snail Compatibility 

Keeping snails with opae ula shrimp becomes a problem because of their contrasting feeding habits. Snails require a lot of food, and when you are supplying food to them, you are indirectly feeding the shrimp, too, as both of them live in the same tank.

In such a case, you have to add proper filtration to the tank- a condition unnecessary for the opae ula shrimp. 

Some expert aquarists often keep Malaysian Trumpet Snails with the red shrimp. In such a case, you have to give the snails a small amount of food not to populate the tank. Pipipi and Nerite snails can be kept with the opae ula shrimp. 

To be honest, it is better to keep the red shrimp in a “species only” tank. 

If you own a blue velvet shrimp then you need to check out this article Blue Velvet Shrimp – Care Guide


Can Opae Ula live in freshwater?

Opae ula needs brackish or salty water for survival. If you keep them in freshwater, they won’t survive for an extended period and become unable to reproduce. 

What does Opae Ula eat?

Opae ula eats algae, blanched plants or veggies, and diatoms. 

How often do you feed opae ula? 

You can feed opae ula once every two weeks or one month. 

About the author

I'm Gulshan, a passionate pet enthusiast. Dive into my world where I share tips, stories, and snapshots of my animal adventures. Here, pets are more than just animals; they're heartbeats that enrich our lives. Join our journey!