Sulawesi Harlequin Shrimp – Detailed Guide: Care, Diet, and Breeding

Sulawesi Harlequin Shrimp (Caridina woltereckae) – Detailed Guide Care, Diet, and Breeding

Caridina woltereckae (also known as the Sulawesi Harlequin Shrimp) is a relatively rare dwarf shrimp species that a lot of hobbyists would like to acquire because of its elegant and unique coloration. Sulawesi Harlequin Shrimp can be a gorgeous centerpiece in a tropical aquarium.  There is one problem though – these shrimp require very specific care.

So, if you are new to this hobby, please, resist an impulse buy. Sulawesi Harlequin shrimp are not for beginners, they are more difficult to keep compared to most other shrimp species.

If you are interested in keeping Sulawesi Harlequin shrimp as aquarium pets or want to learn more about these interesting creatures, this care guide will tell you everything you need to know about them, including their behavior, feeding preferences, ideal tank setups, and how to care for them.

Warning: Currently, Caridina woltereckae has become under threat due to overharvesting for the aquarium trade, pollution, and invasive fish species. So, keep that in mind, if you decide to buy and keep them as pets.

Quick Notes about Sulawesi Harlequin Shrimp

Name Sulawesi Harlequin Shrimp
Common Name
Harlequin Shrimp, Sulawesi shrimp
Scientific Shrimp Caridina woltereckae
Tank size (minimal – optimal) 5 – 10 gallons (~20 – 40 liters)
Keeping Difficult
Breeding Medium-Difficult
Size up to 0.7 inches (~1.8 cm)
Optimal Temperature 83.6 – 84.5 °F (28.7 – 29.2 °C)
Optimal PH 8.4 – 8.5
Optimal GH 6 – 7
Optimal KH 4 – 5
Optimal TDS 146 – 175 µS/cm or 75 – 90 ppm
Nitrate Less than 10 ppm
Diet Algae eater/omnivore
Temperament Peaceful
Life span 1 – 2 years
Color Form Reddish (or dark-brown) bands around the carapace

Taxonomy of Sulawesi Harlequin Shrimp

In 2009, the taxonomy of freshwater shrimp from Sulawesi was partially revised. As a result, two new species, Caridina woltereckae and Caridina mahalona, were described and illustrated in details.

Caridina woltereckae got its scientific name after the German naturalist Eva Roth-Woltereck (1911 – 2003), who described several species of the atyid shrimp from Sulawesi in the 1930s and did her doctorate on these animals.

Origins, Natural Habitat of Sulawesi Harlequin Shrimp

Natural Habitat of Sulawesi Harlequin Shrimp (Caridina woltereckae)Caridina woltereckae is endemic to Lake Towuti, the largest of the five connected lakes, within the Malili lake system. 

These shrimp are only found on a hard substrate, mainly between small rocks in shallow water, and large rocks in deeper water (below 3 m or 10 ft.).

According to collectors, when disturbed, Sulawesi Harlequin shrimp try to escape side or downwards rather than in other directions, but mostly stay attached to rocks.

Description of Sulawesi Harlequin Shrimp

Sulawesi Harlequin Shrimp (Caridina woltereckae) – Detailed Guide Care, Diet, and Breeding
photo by Chris Lukhaup

This is a small species of freshwater shrimp that generally reaches 0.7 inches (or 1.8 cm) in females. Males usually do not grow larger than 0.6 inches (~1.5 cm) in length.

They have short-stalked dark brown eyes that are protruding from their carapace. The rostrum is well developed and very long.

Sulawesi Harlequin shrimp have 3 three distinguishable transversal reddish (or dark-brown) bands around the carapace. The first 2 bands usually joint at dorsal surface to form a n-shaped band in lateral view.

The body is either transparent or slightly pigmented with white. The legs usually have red tips or are colorless.

Lifespan/Longevity of Sulawesi Harlequin Shrimp

Once a proper aquarium is set up and optimum living conditions are met, Sulawesi Harlequin shrimp can live up to 1.5 years in captivity.

Difference between Caridina Woltereckae and Caridina Spongicola

There is considerable confusion surrounding the taxonomy of many species of Caridina. Unfortunately, we have the same problem with Caridina woltereckae as well.

For example, the color morph of this species closely resembles Caridina spongicola, so both species can easily be misidentified. Thus, it is not surprising that some pet stores can accidentally sell this species under other names.

  Caridina woltereckae
(Sulawesi Harlequin shrimp)
Caridina spongicola
(Sulawesi Harlequin sponge shrimp)
Location: In all parts of Lake Towuti of Sulawesi, Indonesia In the outlet bay of Lake Towuti of Sulawesi, Indonesia
Average size: 0.7 inches (or 1.8 cm) 0.6 inches (~1.5 cm)
Color: Vivid or contrastingly colored Inconsistent
Color pattern: Distinctive sidelines Fuzzy sidelines (almost don’t exist)
Habitat preferences Rock dweller Unexceptional occurrence on sponges
Rostrum Longer rostrum (reaching beyond end of scaphocerite (looks like a “fang)) Shorter (reaching to or slightly beyond the third segment of antennular peduncle)

Note: It is extremely important not to confuse these species because Caridina spongicola (Sulawesi Harlequin sponge shrimp) is the only freshwater shrimp that associates with in a yet undescribed freshwater sponge of the suborder Spongillina. They use this commensal symbiotic relationship to survive. Therefore, keeping them in aquariums can be extremely difficult.

Difference between Caridina Woltereckae and Caridina Spongicola
photos by Chris Lukhaup and K. Zitzler

Behavior of Sulawesi Harlequin Shrimp

Sulawesi Harlequin shrimp are completely peaceful creatures; they will do not even bother anybody in the tank.

They are also very shy. Being nocturnal animals, their activity starts at sunset and gradually stops before sunrise.

This lifestyle is easily explainable because due to their small size, many predators could take advantage of them whilst feeding.

Interesting fact: On a 24-h cycle, dusk is a period in which algae had maximum nutrients at the end of the photosynthetic period corresponding to profitable conditions for grazers to feed at the end of the light period.

Sulawesi Harlequin shrimp are social. They prefer the company of their species members. It makes their life richer and less stressful. In addition,

Larger colonies often have more active members, which can be seen venturing out from hiding and showing off more often. So, ideally, Sulawesi Harlequin shrimp need to be kept in large groups.

Features:

  • Social: Yes
  • Active: At night
  • Peaceful: Yes

Feeding Sulawesi Harlequin Shrimp

Like most freshwater shrimp, Sulawesi Harlequin shrimp are scavengers and omnivores. Basically, they will eat just about any food they manage to find.

Therefore, in a well-established (matured) tank, they usually can find enough supply of food (algae, debris, biofilm, etc.) by themselves.

Nonetheless, in order to keep them healthy and happy or if you want to enhance their coloration, it is definitely recommended to supplement their diets with vegetables and other commercial foods such as (links to check the price on Amazon):

Providing them with dry leaves and blanched vegetables (like carrots, sprouts, spinach, cucumber, zucchini, etc.) will also help them to get all the necessary microelements necessary for molting.

Tip: It is better to feed them in the evening. Sulawesi Harlequin shrimp are nocturnal animals. So, they come out and feed better when the lights are turned down/off, as compared to when lights are on.  

Calcium Supplements

Like all crustaceans, Sulawesi Harlequin shrimp have a multi-layered exoskeleton hardened by calcium salts except around the joints where the integument is soft and flexible.

Therefore, it is absolutely important to make sure that they get enough calcium (for the exoskeleton). We can do that by regularly feeding specialized invert foods or calcium-rich vegetables. 

Calcium plays a huge role in any shrimp. Therefore. I highly recommend reading my article “How to Supplement Shrimp and Snails with Calcium”.

How Often to Feed Sulawesi Harlequin Shrimp?

If you have a matured tank (with algae and biofilm), you can feed them once in 2 – 3 days. It will make the shrimp-keeping process both inexpensive and highly convenient.

Remember it is better to underfeed than overfeed!

Without any doubt, overfeeding is one of the biggest causes of death for dwarf shrimp! It is even worse for very sensitive species like Sulawesi Harlequin shrimp.

Uneaten food and organic waste can quickly decompose and cause an outbreak of infections, parasites, ammonia, and nitrate spikes are caused mostly by an excess of food and organic waste.

It is absolutely important to check how much you are feeding the shrimp.

You can read more about it in my articles:

Sulawesi Harlequin Shrimp and Live Plants

Do not keep them in planted tanks.

Generally, I am all in favor of keeping shrimp with plants but not this time.

No, Sulawesi Harlequin shrimp do not eat healthy plants.

The reason is that in planted tanks pH, levels often fluctuate a little. When the lights are off, plants stop taking in CO2 and producing oxygen. As a result, we get more carbonic acid in the water. The more carbonic acid present in your water the lower your pH will become.

Sulawesi Harlequin shrimp are very delicate and even small fluctuations will create additional risk.

Caring and Keeping Sulawesi Harlequin Shrimp

Sulawesi Harlequin shrimp should not be attempted by novice shrimp breeders. They are not the easiest Sulawesi species.

These shrimp require a specific system that is focused on their needs. Therefore, if you want to create the best possible conditions for them in our tanks, here are some care guidelines to help you out.

First of all, it is important that you cycle your tank before bringing shrimp home. However, the mere fact that your tank is cycled is not enough for this species.

Wait at least a few more weeks, let the tank develop a stable eco-system with biofilm and algae as a natural source of food for your shrimp.

Tank Size:

The minimum recommended tank size for Sulawesi Harlequin shrimp is a 5-gallon (20-liter) tank. Ideally, a 10-gallon tank (40 liters) will suit them way better.

It is all about stable water parameters. Unfortunately, it can be really hard to achieve in small tanks even for experienced aquarists. Considering their small size, a 10-gallon (40 liters) tank can easily accommodate at least 40 – 50 Sulawesi Harlequin shrimp.

Related article:

Water Parameters: 

Important:  If you are buying captive-bred (for several generations) Sulawesi Harlequin shrimp you need to find out the water parameters they were bred in. If you can’t find this information, you will have to take the risk and presume that the breeder kept them in water parameters that are close to the natural ones. So, you will have to replicate the water from Lake Towuti.

Related article:

 The average parameters of Lake Towuti are:

Temperature: 83.6 – 84.5 °F (28.7 – 29.2 °C). You will need a heater.
These shrimp prefer a warm habitat and can get shocked if the temperature drops below 77 °F (25 °C).

Hardness: GH 6-7 and KH 4-5.
Sulawesi Harlequin shrimp do not like hard water.

pH: Optimal water pH should be provided for this species around 8.4 – 8.5

TDS: 146 – 175 µS/cm or 75 – 90 ppm

Oxygen: 7.15 mg/l. Potentially, you will need an extra air pump to keep the water oxygenated. Low oxygen can be a real problem.

Water type:

Sulawesi Harlequin Shrimp (Caridina woltereckae) – Detailed Guide Care, Diet, and Breeding Sulawesi Mineral 8.5Keeping Sulawesi Harlequin shrimp in tap water is almost impossible. Yet so many shrimp keepers make this terrible mistake.

It is definitely and highly recommended to use RO/DI water with a special supplement to mineralize it.

Sulawesi Mineral 8.5 (link to Amazon) was developed according to the results of a scientific analysis of water originating from the water of Lake Towuti. It will provide all important minerals and trace elements and improve their health, wellbeing, and coloration.

Lighting:

Sulawesi Harlequin shrimp are nocturnal. Basically, they do not really depend on the light.

Substrate:

Sulawesi Harlequin shrimp prefer rocky substrate with some sand.

Filters:

There are no special requirements as well. As long as you have got the filter that works great with the size of the tank you have got you will be fine.

Personally, I would always recommend using sponge filters or matten filters for any small tank setups.

These filters are cheap, easy to maintain, and clean; they provide a lot of surfaces to graze on.  

Related article:

Decorations:

In aquariums, decorations play an important role for the Sulawesi Harlequin shrimp.  They provide:

  • more surface area for algae and biofilm growth,
  • hiding places (shelter and protection) and minimize stress to your shrimp. 

This is also crucial for the molting process! Therefore, there should be plenty of dark areas for them to hide in and these should be created out of rocks, PVC pipe, plastic tunnels, etc.

Important: I would be careful with the large pieces of driftwood in the Sulawesi Harlequin shrimp tank. Because of the tannins, you may have some pH fluctuations. Obviously, you do not want that with such a fragile species.

Acclimation:

Before putting Sulawesi Harlequin shrimp into your tank do not forget to carefully acclimate them for a few hours.

Do not rush the process! Do it very slowly to prevent any unnecessary stress.

Be careful with chemicals like copper (read more). Like all crustaceans, Sulawesi Harlequin shrimp do not tolerate copper-based medications. 

Breeding Sulawesi Harlequin Shrimp

Although it is not easy to breed Caridina woltereckae in captivity, it is still possible. They usually do not breed until the environment is optimal for them.

The life cycle starts with mating. This is a very brief (a few seconds) and potentially dangerous processes for the females.

The point is that shrimp females need to molt (shed their old exoskeleton) before spawning. It makes their cuticles soft and flexible, which makes fertilization possible. Unfortunately, it also makes females very vulnerable.

Ovigerous females can carry between 20 – 30 eggs. The medium egg size is around 1 mm. Generally, it takes them 3-4 weeks to hatch.

Sulawesi Harlequin shrimp do not have larval stages, so what emerges from the egg is a tiny copy of the adult shrimp.

Balance their feeding with powdered food. 

Baby shrimp do not move around as big shrimp do. Therefore, if they do not find enough food there they starve to death.

For more information, read my article “How to increase shrimplets survival rate?”.

Sulawesi Harlequin Shrimp and Suitable Tankmates

Because of the specific requirements, the ideal situation for the Sulawesi Harlequin shrimp is a species only tank with hardy snail species like Rabbit snail (Tylomelania), as they have quite similar living conditions.

It is not recommended to keep them even with some other popular Sulawesi shrimp (for example, Cardinal shrimp (Caridina dennerli) because these two species prefer different pH.

In Conclusion

These shrimp are cute, unique, and simply gorgeous! Unfortunately, there are just two main problems:

  1. They are pretty rare.
  2. Sulawesi Harlequin shrimp are not for beginners. Along with monitoring your water parameters, you also must closely monitor the temperatures of the tank. You cannot allow any fluctuations.

References:

  1. Caridina spongicola, new species, a freshwater shrimp (Crustacea: Decapoda: Atyidae) from the ancient Malili lake system of Sulawesi, Indonesia. The Raffles Bulletin of Zoology. 2006.
  2. Freshwater shrimp–sponge association from an ancient lake. Biol Lett.2007 Jun 22; 3(3): 262–264.
  3. Radiation of endemic species flocks in ancient lakes: Systematic revision of the freshwater shrimp Caridina H. Milne Edwards, 1837 (Crustacea: Decapoda: Atyidae) from the ancient lakes of Sulawesi, Indonesia, with the description of eight new species.  2009. The Raffles Bulletin of Zoology57(2):343-452.
  4. Sulawezi garnalen. Tekst: Kim de Graeve – bewerking HE-redactie. Vormgeving: Zilverhaai Beringen.
  5. Biota Perairan Terancam Punah Di Indonesia: Prioritas. Perlindungan. 2013.
  6. Aquatic biodiversity hotspots in Wallacea: the species flocks in the ancient lakes of Sulawesi, Indonesia. by Cambridge University Press.
  7. Cai, Yixiong, Wowor, Daisy, & Choy, Satish. (2009). FIGURE 3. Caridina woltereckae, new species A in Partial revision of freshwater shrimps from Central Sulawesi, Indonesia, with descriptions of two new species (Crustacea: Decapoda: Atyidae). In Zootaxa (Vol. 2045, pp. 15–32). Zenodo.

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