On Keeping Softwater Caridina Shrimp
submitted by Brock Burch
August 2020
I have only been in the hobby for about 4 years, yet many of my peers consider me an authority figure on certain subjects. I have delved deep into the world of the aquarium hobby and familiarized myself with subjects of water chemistry, advanced plant care, and, my biggest passion, the keeping and breeding of dwarf shrimp. Of particular interest to me are those of the genus Caridina.
Shrimp keeping has exploded in popularity since the late 2000’s. Dedicated breeders in Germany, Hungary, Singapore, Taiwan, Japan, China, and Thailand have stabilized and perfected beautiful and colorful strains of shrimp. What once cost 4 figures for a male/female pair can now be purchased at $5 each thanks to those pioneers of the shrimp-keeping hobby.
It seems that every freshwater aquarium owner loves these colorful, active, and easy-to-breed shrimp, and many get their toes wet (no pun intended) with the popular Neocaridina davidi strain, “Red Cherries”. Cheap, hardy, gregarious, and prolific breeders, they remain the most popular freshwater shrimp commonly kept in the hobby.
However, more advanced hobbyists know that the real hidden treasures are the Caridina shrimp, and in particular those known as “crystals” and “Taiwan bees”. I will delve into the biology and care of these beautiful animals that are becoming evermore refined into more complex and beautiful strains.
Taiwan bees, of the genus Caridina, are more finicky when it comes to their care. Unlike their Neocaridina cousins, Caridina need very soft, acidic water. What this means is, especially here in the US, most people’s water is just too hard to keep them. In my experience, they usually don’t last more than a few weeks in hard, alkaline water. I will get into the specifics of their needs shortly, but chances are if you live somewhere in the US, you have hard, alkaline water.Taiwan bees need rather specific conditions to truly thrive. For hardier breeds, such as Crystal Reds and Crystal Blacks, a pH of less than 7.0 is required, with a general hardness of between 4 and 7, and a carbonate hardness as close to 0 (zero) as you can get it. These shrimp have molting issues in hard water, and also will not breed. For more delicate strains such as Zebra Pintos, Blue Bolts, and King Kongs, a pH as low as 5 is recommended, with a general hardness of 3-5 and again, a carbonate hardness as close to 0 as possible. These shrimp tend to be more expensive, and the lower pH recommended to prevent bacterial and fungal infections. However, not everyone is keeping shrimp that can cost $50 a piece (Skyfish Boas cost an astounding $1200 each). We will focus on the easier Crystal varieties which includes Crystal Reds, Crystal Blacks, and Golden Bees.
When setting up for these shrimp, you first need to determine the parameters of your tap. Chances are you are not blessed with the magic numbers for these shrimp, so most people will have to resort to using reverse-osmosis (RO) or distilled water and add minerals to it to reach the ideal ranges. This sounds tedious but all I do is mix a small spoonful of shrimp salts into a 1 gallon jug of water once a week (it would be more or less depending on the volume of your tank). For Crystal Reds and other softwater Caridina, you need a salt that only raises the general hardness (GH) of your water, but not carbonate hardness (KH). You will also need a GH and KH test kit, as well as a TDS pen, which reads the total dissolved solids (TDS) of your water. You can get a general idea of what your GH to TDS ratio is over time; at a TDS of 90 my GH is approximately 5 degrees. These numbers depend on the brand of salt you use, and even the batch-to-batch ratios.
The next most important thing when keeping these shrimp is your substrate. In order to keep the pH acidic and the water soft, a buffering substrate is required. Commonly known as “aqua soils”, these soil/clay based substrates keep water acidic, remove carbonate hardness, and maintain a low general hardness as well. They often can leach ammonia into the water, but that can be an advantage; by leaching ammonia, you can cycle a tank with no fish, no dosing ammonia, no adding fish food, etc. Not all soils leach ammonia, but you should still properly cycle a tank before adding any living things. With all shrimp, it is also important to allow the tank to mature and become established for several weeks or even months after it cycles. This ensures enough biofilm (a layer of bacteria and other microbes that grow on surfaces in a tank) and algae has accumulated to keep them well fed.
Keep in mind the longevity of aqua soils is around 2 years (if following the steps and using RO/distilled water), so once you hit the year-and-a-half milestone of a tank, it is time to consider setting up another one to cycle and mature so you can transfer your shrimp safely. Once the buffering capacity is depleted, it no longer functions to keep your pH low, and you will see a decrease in breeding and generally less activity out of your shrimp.
For the more finicky strains, to maintain a very low pH and soft water, some breeders use akadama, which is a special potting soil used for bonsai. This substrate can pull pH down as low as 5.0, and yet Taiwan Bees thrive in these conditions. Admittedly I have yet to use this substrate, but plan to in the future when keeping the more rare, less hardy strains. Plants are an integral part of a shrimp tank. While any and all plants are beneficial, those of particular interest to shrimp keepers are floating plants and mosses. Floaters such as Amazon frogbit, dwarf water lettuce, and Salvinia natans pull nutrients from the water, keeping nitrates low, as well as forming an inverted lawn of roots for shrimp to hide and forage. Likewise, this fin fluffy texture of mosses provides surface area for shrimps to feed and for babies to hide and mature. Aqua soils, while providing the perfect conditions for shrimp, are also the best substrate for plants. Plants also prefer more acidic water, so you can expect great growth.
Lighting is generally only important for two things: plant health and growing algae. I have seen tanks where the walls look like green shag-carpet; this is perfect for shrimp and many breeders strive to provide plenty of vertical green pasture for their little “cattle” to graze. Algae of any kind is welcome in shrimp setups (unless they are primarily for display), although I have heard anecdotal tales of shrimp becoming entangled in string algae that grew too unruly…
When it comes to feeding your shrimp, it’s a varied and interesting topic. Truth be told, there isn’t much your shrimp won’t eat, or in some cases can’t eat. In the wild they live as detritivores, so feed on algae, mulm, leaf litter, and organic matter. I feed my shrimp high quality commercial shrimp foods, as well as fresh vegetables such as zucchini and romaine lettuce. They also love fruits, but feed in moderation as the high levels of sugars in fruit can fowl tank water. That being said, watermelon was a big hit with my colonies. Hardwood and non-citrus fruit tree leaves, dried and collected away from high traffic areas, are long lasting and sustainable sources of food for shrimp. I have had lots of success with oak, magnolia, persimmon, and the ever popular Indian almond leaf. They also provide beneficial tannins, keeping the pH low and preventing the growth of harmful fungus and bacteria. It is advisable to feed a source of protein once a week to help with egg production and prevent cannibalism. I usually feed frozen bloodworms which my shrimp love.
When doing maintenance on a Caridina tank, it is recommended to only do water changes when necessary. Unlike fish tanks, 50% water changes weekly can potentially kill these shrimp. They need their water conditions to remain stable, and when something changes too abruptly, such as temperature,hardness, or pH, it triggers them to molt. These premature molts can cause a lot of stress to the shrimp,and sometimes they cannot shed their outer molt at all, resulting in a failed molt; basically, the shrimp is trapped in it’s old shell like a straitjacket, and will almost invariably die as a result. While I was doing 20% water changes weekly, I now only perform 20% water changes when the TDS is around 10 ppm higher than my target range of about 90; so maybe twice a month. Throughout the week, I also top off evaporation with distilled water to ensure parameters remain stable and my shrimp are happy.
Avoid keeping most fish and crayfish with your shrimp, as well as larger freshwater crabs. Turtles, axolotls, and other aquatic reptiles and amphibians would decimate a population, so avoid at all costs (not that anyone with common sense would keep shrimp that cost $5 each with a hungry turtle). Almost everything loves the taste of shrimp, and even very small fish such as guppies or neon tetras will happily make a meal out of small shrimp. Most snails are safe with shrimp but avoid assassin snails as I have heard from multiple sources that they can potentially kill small shrimp. Larger aggressive shrimp such as whisker shrimp and freshwater prawns will kill and eat them.
Safe tank-mates include other species of dwarf shrimp (provided they can live in the same water parameters), most snails, freshwater clams, otocinclus, and small plecos.
Now the most exciting part of keeping Caridina: breeding them. If you have met their basic needs in the previous step, all it takes is time. Keep the temperature in the low 70s if possible, offer plenty of high quality food a few times a week, and keep their water clean, and within a few months of starting a tank you will see babies everywhere. Babies are miniature copies of the adults, and are a joy to watch. Keeping the shrimp in a tank by themselves ensures the most babies survive, and also ensuring that your filtration is covered if not using a sponge filter (the safest method). I use stainless steel mesh intake guards, too small for babies to fit through, on the intake of my canister filter. While these guards don’t harbor biofilm for shrimp to feed on, they don’t become clogged and are easier to clean.
The lifespan of these shrimp is between 1 and 2 years, and it is recommended to introduce new members once a year to ensure there is no genetic bottle-necking caused by inbreeding. Many keepers “cull” less desirable shrimp, but that is a term that doesn’t necessarily mean killing them. Shrimp with poor coloration or genetic defects can be kept in their own tank, where they can live out their lives content and well-fed, while the shrimp with richer colors are continually bred to strengthen their line.
Every now and again, an interesting new color morph appears. Shrimp keepers isolate these unusual genetics and breed them, hoping to work out the kinks and produce beautiful, valuable new lines. Morphs such as Dragon Blood, Boa, Nanacy Galaxy Pinto, and Mosura Blue Steel, can fetch hundreds if not thousands of dollars for viable male/female pairs! While these strains may take several generations to isolate and refine, it is well worth the work, and many breeders consider it a labor of love.
Shrimp keeping is a fascinating field of the aquarium hobby with it’s own idiosyncrasies that make it, at times, very unlike fish keeping. It is both challenging and rewarding and, if you have a good understanding of the biology and chemistry involved in keeping aquatic animals, is quite easy. With patience, attention to detail, and a strong foundational knowledge of aquaria, anyone can keep and breed these colorful crustaceans.
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