My experience of keeping and breeding volcanic shrimps
Opae Ula (Halocaridina rubra)

 

About a year ago I came across a description of the “ecosphere” - a closed ecosystem in which, according to the authors, all components exist in complete biological balance. This ecosystem is a sealed glass bulb, completely isolated from the outside world, it’s located in natural light and is balanced in such a way that there are higher aquatic life in symbiosis with lower plants - algae, and all parts of this ecosystem are in strict equilibrium with each other. The mechanism was described as follows: shrimps inside the sphere eat algae that develop on the surfaces of a sphere: on the walls, on the ground, on a piece of driftwood. During the life shrimps produce small amounts of waste products: carbon dioxide, ammonia, nitrites and nitrates, which, in turn, are a nitrogen fertilizer for plants (in this case - for the lower algae). They provide nutrition, along with the results of photosynthesis - the formation of chlorophyll of carbon dioxide in natural lighting. Following the laws of the nitrogen cycle, nitrite are converted into less toxic nitrate by nitrifying bacteria that inhabit the soil and organic surfaces (piece of driftwood), and nitrates are absorbed by lower algae. The algae, in turn, produce the light necessary for life shrimp oxygen, etc.

I was surprised and puzzled. As a person skilled in maintaining the biological balance in open ecosystems - aquariums - I not only did not deny the possibility of the existence of closed ecosystems, but emulated such systems in my aquatic rooms not once, creating aquariums that require virtually no interference for operation. My surprise was based on the fact that a stable ecosystem can exist being of significant size. The smaller the tank, the more difficult it is to establish biological equilibrium, - this is the rule. In a large aquarium significant variations of basic parameters are possible, such as water temperature, pH, hardness, level of dissolved substances. For example, if a fish dies and go unnoticed in a small aquarium, its decomposing will lead to increase in ammonia levels and rapid growth of bacteria that cause a decrease in dissolved oxygen in the water and similar processes. These processes will not be so significant in a large aquarium. The same amount of ammonia and bacteria in a large aquarium will cause only minor changes that will be easily eliminated by the ecosystem itself: snails consume a significant amount of decomposing organic matter, and all that remains that is not eaten will be processed by plants, bacteria and filters. Ecosphere of 2-3 liters in size, in my opinion, has no right to exist; the biological balance in such a small volume cannot be sustained. Nevertheless, reviews that I’ve read stated that such closed “ecosystems” successfully exist, and shrimps in them remain alive for 2 to 3 years. The only explanation for this phenomenon in my view is the uniqueness of shrimps that leave in the sphere.

I browsed the Internet in search of information about the shrimps that are sold in ecospheres, and I was impressed with what I’ve learned. Although I never had any experience with the inhabitants of salt and brackish water, I decided to buy these shrimps. As I found out on the Internet, Hawaiian red shrimp (other names – “volcanic shrimp”, “Opae Ula” in the Hawaiian language, scientific name Halocaridina rubra) are characterized by their incredible adaptability to environmental conditions. In the wild they live in the crevices in the lava of volcanoes, where water salinity varies from almost fresh in rainy season to full salinity in the dry period. These shrimps also tolerate temperature variations from 50 to 90 F (10 to 33 C), the lack of food for many months and even years (!). During hungry period they can decrease in size (that is, a new shell, worn them when molting is less than the previous one). The most amazing discovery for me was that the Hawaiian volcano shrimp can live up to 20 years.

I searched the Internet and found just one seller in Hawaii that sells wild-caught shrimp. I have had a negative experience acquiring other "wild" shrimp in the past, but I was intrigued and impressed with their vitality, so I decided to buy. The seller shipped 50 shrimps in a small amount of water – literally about 5 ounces (150 grams), insulation of the package was almost nonexistent. I was lucky: shrimps were alive despite such extreme shipping conditions.

Now my goal was to create the right conditions for them, and that's what I want to share with you in detail to keep the reader from the possible mistakes, some of which I made myself.

Salt

Being in discus breeding hobby, I used sea salt from Home Depot (“Solar Salt”) that is used for softening tap water for washing (adding the salt in the water in the aquarium with discus is a common practice of discus breeders. Salt inhibits the growth of harmful bacteria and improves slime producing in discus, which is especially important during the feeding of discus babies, and promotes healing of wounds). Label on the bag have read that the salt is a common sea salt obtained by evaporation of sea water in the open sun. Its non-toxicity has been tested by me thousand times on discus. I took the right amount of salt and dissolved it in distilled water until the salinity of 15 g/l (SG 1,010) was reached. I left shrimps swimming in the open jar in the water in which I received them, netted out three "kamikaze" and put them in the freshly prepared water. Shrimps were swimming normally within an hour or two, but then they became apathetic and stopped swimming. I touched them with a stick and found that they were barely alive. I immediately returned them to the jar with other shrimps. "Kamikaze" came to life and began to behave in the same way as the rest of the shrimp in just a few minutes. It was obvious for me that the problem was with the new water that was bad for the shrimps. I took another salt from Wal-Mart that is sold under the name Aquarium Salt. The result was exactly the same as with the salt from Home Depot, with the difference that "kamikaze" were put in the new water overnight and found dead in six hours. I have carefully examined them with a magnifying glass and did not see any signs of life. However, I did not throw them out, but transferred in the jar to the other shrimp. I was surprised when, after half an hour they showed signs of life, and an hour later they began to swim. I lost only one shrimp.

In the Internet I haven’t found any confirmation or disproof that salt which I have tried to use is normal sea salt and can be used in a marine aquarium. Next day after work I visited a pet store and bought a pack of salt for salt water aquariums. This time there were no problems, and in two days after the arrival my new inhabitants have moved to the new residence.

Plants

In my conception, aquarium looks incomplete without plants, and I tried to adapt a variety of aquatic plants to water salinity of 15 g/l. Java moss was alive for two weeks, Elodea - a week, Java fern - a few days. Bacopa lasted longest. It even developed a few roots and leaves, but a month later began to wither and eventually died. I was quite resigned to the fact that in my tank with Hawaiian shrimps will be no live plants when I found a small patch of filamentous algae. This was not the alga that appears in freshwater aquariums. Its bristles were shorter and thicker, forming a “brush”. Soon I found that this alga is growing quickly, and shortly it formed a pretty decorative tight ball. A year later, the ball has reached a diameter of 6-7 inches (15-16 cm), and I divided it in half, after setting up a new aquarium in my office at work.

I can’t say that with hair algae aquarium looks very decorative, but still it was better than without plants.

Gravel

At first I set an aquarium with quartz neutral gravel. Then I got an idea to add to the aquarium landscape of live rock. This is known that over time, porous rocks are colonized by beneficial bacteria, which begin to take active part in the nitrogen cycle of the aquarium, in other words, they begin to act as biofilters. Thinking of a porous material, I suddenly remembered that I’ve seen bags with red lava in Home Depot, which is used in home landscaping. I remembered that in nature Hawaiian shrimps live in lava cracks filled with mixture of sea and rain water. I was not sure of the complete inertness of red lava, so I set up a tank with lava bottom inhabited with low-value freshwater shrimps. Shortly I’ve got the proof the lava is harmless and built “mountains” of pieces of purple-red lava, and my aquarium have got a very decorative look.

Other inhabitants

The only inhabitants of the aquarium with a salinity of 15 g/l, except shrimps, are Nerite Snails. I was hoping that the salinity of 15 g/l is right for Nerites’ eggs to develop, but they never hatched. As in freshwater aquarium, their eggs remain indefinitely in “sleep” phase, not evolving. Once I found a tiny snail on the glass, then I found a few more. I was sure that eventually some of Nerits hatched, but after a while, I found that I was wrong: the snails turned out to be regular Trumpet snails which perfectly adapted to salt water. They couldn’t compete for food with shrimps, therefore, they reproduce slowly, and their number stays small.

Feeding

Taking into consideration that Hawaiian shrimps live in ecospheres for months and even years without any food, I knew that feeding them is not really priority number one in freshly established tank. However, I didn’t want my shrimps just survived; I wanted them happy. Information from the Internet have been inconsistent: many people recommended feed them with tiny amounts of Spirulina powder – size of a match head - once every 2-3 days. That's what I did for a while, but then began to experiment with other types of food.

We must remember that Hawaiian shrimps are herbivorous. I crushed ramshorn snail and put it into the aquarium. My freshwater shrimps find crushed snails delicious, but Opae Ula ignored them completely.

I make frozen food for my freshwater shrimps of following ingredients: boiled zucchini, carrots, green beans, spinach, green beans, raw saltwater fish, raw shrimp, chlorella and spirulina powder, vitamins. I blend ingredients in a food processor, and then fix the pasty mass with agar-agar. Then I make 5-6 mm thick flat packs in plastic bags, freeze them and store in freezer. My shrimps eat 200-250 gram of this food for one feeding. This food was offered to Hawaiian shrimps, and they liked it. After that they were positive to virtually any vegetable food that was fed to the rest of my shrimps: scalded spinach and Romaine Lettuce, cooked zucchini, cooked or canned green beans. Boiled zucchini was initially inconvenient to use: slices of zucchini would not sink in salt water. This inconvenience disappeared over time as the number of shrimps in the tank reached hundreds. They sat on the slice until it was sunk, and then it was completely covered with the mass of shrimps.

So, I was offering to my shrimps a variety of food, but still kept feeding them with Chlorella and Spirulina powder as well: there were larvae floating in the water that were not able yet to pick food from surfaces in the aquarium. I have observed the larvae for hours using special magnifying glasses. I saw enough to learn that for feeding larvae need a nutrient suspension in the water. Spirulina powder is optimal for this purpose: at sizes of 20-40 micron particles of Spirulina were readily eaten by larvae. This suspension stays in the water for long time, and settled is immediately eaten by adult shrimps.

Watching how Hawaiian shrimps swim, I drew attention to the fact that they tuck up their legs, unlike other shrimps. I made the assumption that they developed this feature to reduce the water resistance, and thus, to save energy. However, watching feeding larvae, I zoomed in adult shrimps as well and found that at this time they don’t tuck up legs. On the contrary, they were very actively moving with the first two pairs of legs, those with claws. Suddenly I realized that these movements are actually the process of eating on Spirulina. It turns out that even adult shrimps can eat food suspended in water.

Now I feed Hawaiian shrimp with the same food as all the others. Their main food is zucchini, green beans and my home maid frozen food. In addition, one or two times a day, I add a pinch of powdered Spirulina to the aquariums.

Reproduction

Although Hawaiian shrimps have a larval stage after hatching from eggs, breeding them is not difficult, because the development of the larvae do not require special conditions, as in the absolute majority of shrimps with the larval stage of development (e.g., Amano shrimp, Pinocchio or Ninja shrimps).

Despite the small size of adults (15-17 mm), larvae of Hawaiian shrimps are quite large - about 3 mm in length. However, they are also more “chunky” than, for example, larvae of Amano shrimps. Female are berried for 3-4 weeks, then larvae hatch. The process of hatching is rather long and is easy to observe: a bunch of eggs becomes loose, and the hatched larvae continue to hang on my mother for a few hours before they go to float freely. Number of eggs in clusters is ranging from 10-12 to 25 and more, depending on the age and size of the female.

Also, in my opinion, the frequency of females becomes berried, and the number of eggs directly depends on keeping conditions and the quality of food. When I was feeding shrimps with small amounts of Spirulina, there were just 2-3 berried females and 15-20 larvae in the tank with 300 shrimps. When I started feeding them with varied food, in the same aquarium has been observed more than 10 berried females and over a hundred larvae.

This is easy to distinguish larvae of small shrimp: a larva hangs in the water head down and only occasionally jumps when it, for instance, is knocked by a shrimp. When the larva turns into a shrimp, its behavior is totally changed. Its movements become purposeful; it starts to swim head-first, using swimming pleopods. The main difference lies in the fact that most of the time shrimps spending moving "on foot" on surfaces in the tank, while the larvae are able to just hang in the water.

Aquarium maintenance

Keeping Hawaiian shrimp does not require special skills or special diligence. Many aquarists recommend changing 50% of water every half a year, and periodically add distilled water to replace evaporated. This prevents the increasing of water salinity more than the recommended level. Salinity of the water in my tanks is 15-18 grams of salt per liter of water (SG 1,010-1,013). I don’t perform water changes, because quite often I give out, trade or sell Hawaiian shrimps. I replace water from my tanks that I take for shipping shrimps, with fresh water of the same salinity, prepared beforehand in a separate tank. Doing so, I use all aquarium volume every 3-4 months. Shrimps are doing well.

One must be prepared for the fact that in the aquarium with small number of shrimps and in which biological balance has not yet established, walls and other surfaces soon will be covered with a layer of algae. If this is very annoying, you can clean the front glass with aquarium scraper. Presence of snails will help, because they, being much more voracious than the shrimps, will actively clean the aquarium, eating algae. If algae are developing very quickly, you can reduce the time of daylight to 11-12 hours. When the number of shrimps grows, the cleaning becomes unnecessary: shrimps keep all surfaces of the aquarium in perfect condition.

Conclusion

I believe that keeping Hawaiian red shrimps in the hobby has a huge potential because these shrimp are one of the most fascinating and unpretentious creatures on Earth, and they can happily live and breed in areas where keeping of any other shrimp is impossible. They may be content with a small aquarium in an office, where they can easily stand daily fluctuations in temperature and no air conditioning at the weekend, the lack of food during the holidays and even the absence of the owner that left for a vacation or a business trip. Hawaiian shrimps are cheerful and attractive in appearance. They can be kept in a small pot in the kitchen, instilling in kids interest and curiosity in aquatic inhabitants. Finally, these shrimp do not require virtually any investments, as their colony will live for ten years or more, demanding from the owner just a couple of minutes of attention a day.