Most species of zooplankton are relatively easy to culture in a home/hobbyist setting, if we keep in mind a few common traits. These tiny specimens need the same basic requirements our aquatic pets need: Adequate O2/CO2 exchange, available nutrition and waste removal. Gas exchange is acquired by somehow moving the surface of the water to allow CO2 out and oxygen in, easily accomplished by an airline bubble.

I find the latter 2 requirements are met by the same wonderful marine vegetable product: microalgae. A growing pool of a tiny microalga will consume the waste products of the zooplankton species and provide a continuous diet for them at the same time. I have found that most of the species I grow will have live larvae if they are well fed, but will produce cysts if they feel an impending famine coming.

Some species will grow and thrive on alga paste, spirulina powder or even yeast but I find these to be more difficult to maintain adequate water quality. Experiment to find what works for you.

  Artemia is a small genus, encompassing a few species, one of which is marketed as “Sea monkeys”. These tiny shrimp are easily cultivated for home aquarist use. They are readily available in egg/cyst form.

These shrimp grow abundantly in the Great Salt Lake, in Utah. This environment, during the warm months, is a predator-less paradise where they gorge on the abundant microalgae, grow rapidly and reproduce live nauplii.  Because their diet is so abundant in various microalgae, their colors vary, ranging from dark to light red and green.  When the cool weather begins, these shrimp begin producing cysts which are ready to hatch the next spring. The artemia then die, producing a stench smelled for miles.

Knowing this life cycle, it is relatively easy to recreate a system that can provide their necessities: Adequate O2, food and waste removal. I use a 2 gallon glass jar, an airline with a continuous but gentle bubble, live phytoplankton and an occasional drop of ammonia remover. When the microalga is actively growing, it uses the waste products of the artemia, which creates a symbiotic environment for both species. As the shrimp population increases, the microalga population decreases. It is a balance to harvest the shrimp and add more alga, but it is easy to visually see the balance shift. I find it easier for my life to have a culture that reproduces without continually hatching eggs, but I do find I do need to add a new supply of hatched eggs once in a while.

If you feel a continuous culture is not for you, you can de-capsulate the cysts using a 1:3 part solution of FW and household bleach to remove the shell. Just use a covered container to gently toss the eggs in the bleach solution and rinse well when they turn orange. I use a micro sieve to rinse them in. You can use a spaghetti strainer lined with a coffee filter. These eggs are great to spot feed your corals, but will not hatch very easily. The shell is what creates their buoyancy.

Hatching the cysts is easy. A plastic 2 liter soda bottle is easily converted into a hatcher. Cut it in half, invert the top half and place in the bottom, making sure the lid is tight. Place a rigid piece of airline tubing into the bottom and voile: You have  brine shrimp hatchery. I use old water from my tank, and about a teaspoon of cysts. Experiment a bit to find how much bubble flow you need to get the eggs to move. You want enough water movement to keep them from sinking, but not too much that causes them to get pushed up the sides of the bottle out of the water. In around 18-24 hours, depending on the brand and age of the cysts, the cysts will hatch. Unhatched cysts will sink, the shells will float. It is easy to siphon from the middle to get the newly hatched nauplii. A healthy nauplii will swin to a light source if you want to concentrate the hatched and let the rest continue hatching.

Newly hatched brine shrimp are very high in fatty acids while their egg sack is intact, under 12 hours. Once it is consumed, the nauplii will need to be enriched with a fatty acid supplement, or fed a product that can enhance their nutritional value to make them worth our time and efforts. I’ve used both Selco and Selcon products to enrich (coat) with a high fatty acid concentrate, both clog the respiratory track and will need to be fed out quickly before the nauplii expire.

Brine Shrimp

Copepods

There are many species of copepods. Some are harpacticoid, which means they spend part of their life cycle crawling in substrate or on the glass. Some are calanoid, meaning they spend their entire lives swimming pelagically in the water column. Calanoid can be better for this fact, if you are trying to raise fry. The species of calanoid available to the hobbyist is Artacia tonsa. I have found this species to be demanding and fragile. I have a harpacticoid species, Tigriopus californiicus, which I find very accommodating to my reef tanks. It produces millions of tiny snacks that I harvest daily. Again, I use live phytoplankton and a gentle bubble, a few drops of ammonia remover when I remember. This species is reported to be cannibalistic if it’s food supply runs low.

Copepods are very high in nutritional  value and very much worth culturing for those attempting to raise fry. I have read research papers that state copepods will increase viability by enhancing immune systems, and increase survival rates.

Rotifers

“Rotifers are like a grocery sack. All the good stuff is inside”,

  My favorite zooplankton quote is attributed to the past owner of a retail phyto/rotifer product, and I think it is the best way to describe rotifers: an empty shell used for delivering the nutritional phytoplankton inside. While copepods produce their own fatty acids and are nutritionally complete, rotifers are very deficient in nutrition unless “gut loaded”: fed a live alga, an algae paste product or spirulina powder.

Rotifers are easily cultured in a hobbyist setting. Again, adequate water movement to allow oxygen in, CO2 out is important. I find slow, gentle movement works best with this species. I use live phytoplankton to culture them, although when I start a new culture I sometimes gut load the old one to feed out. I have found that non-growing food causes my cultures to decline in status rather quickly, so I do not usually do this unless I have a specific need. Newborn fry do need high levels of proteins and fatty acids, so gut loading a rotifer is a great way to increase the fry’s intake of specific elements. It is also a technique we can use to provide medications.

  A few times, I have had a culture seem to “crash”. In my experience, these cultures rarely die, they just go dormant. If your culture clears its food supply quicker than you can supply phyto for it, harvest it way down until your phyto production can keep up with your rotifer production. It is important to always keep a strong color of your phyto of choice in this water, because once the culture turns to cysts, it takes a while to bring it back. It takes a bit of experience to know when to harvest the culture way down to prepare for a weekend trip or vacation, or just a slow down in phyto production.

Word of warning? If just one rotifer gets in a phyto culture, it will eventually consume the entire vessel. If you grow rotifers and your phyto culture quits growing, hold a clear glass of it up to the light. Chances are great that you will see the little bugs gorging themselves on your favorite alga. Keep a few cultures going of an alga that is not easily replaced. Rotifers really can fly through thin air, leap buildings at a single bound! Because of their incredible rate of proliferation, as an algae lover, I consider rotifers the root of all evil. I do not grow them without a specific fry need. I find brine shrimp nauplii much easier to live with.