John D Hirsch MD

Experienced Reefer
Manhattan Reefs
Zooplankton represent the largest animal biomass on the planet. They occupy a critical base level of the food pyramid but also serve as detrivores in the detritus pyramid. They are responsible for consuming and processing waste into packets that are moved down the waste disposal system to those microorganisms that eventually produce the end products of waste disposal, ammonia and carbon dioxide. A healthy reef ecosystem has a healthy zooplankton population.
Zooplankton available in the trade vary in size from Tigrios (large) to Tisbe (small) and everything in between. They are all have chitinous exoskeletons and molt 7-10 times during their life cycle. That life cycle is generally about 30 days. Females produce egg cases containing 40-100 eggs. Newly hatched zooplankton are called nauplii. Some are warm water breeders others cooler water breeders. Generally, the smaller the organism the greater the number of eggs and egg cases produced. Zooplankton are either benthic (living on the substrate) or pelagic (free swimming). Both are important. Some consume phytoplankton and are mostly herbivores and others are mostly detrivores consuming waste.
Some thoughts on purchasing zooplankton for your reef ecosystem
1. Purchasing a single species of zooplankton, gives you one chance to establish a healthy colony. Purchasing multiple species increases your chances of success.
2. Zooplankton are animals and all animals hunt and consume nutrients. Typical transit times through their digestive tracts can be measured in hours. Purchasing zooplankton in totally clear solutions, that is, without a source of food, means that they are starving. Refrigerating the container will slow their metabolism but likely not extend their life cycle. ?Gut Loaded? means well fed if you are purchasing as a food. Starving zooplankton likely will not produce egg cases and have less than optimal nutritional value.
3. If you see debris on the bottom of the container, it is either a healthy sign of molting gut loaded organisms or dead organisms. A flash light might help you decide. Look for containers with either born on dates or use by dates as again most zooplankton have a 30-day life cycle.
4. Rotifers are frequently seen in zooplankton cultures and can be difficult to differentiate from nauplii. Swimming patterns can help.
5. There is no good reason to dose small amounts of zooplankton and refrigerate the rest. You will have optimal benefit if you wait until dark and add the entire container to either your tank or sump or both, giving them a chance to find hiding places and nutrients to consume.
6. It is a good idea to refresh your zooplankton colonies at least quarterly or more often to ensure a healthy genetic population that will reproduce healthy individuals.
7. If you use a mesh filter sock in your sump, many of the smaller species can pass through, larger species typically don?t.
I have attached photos of a typical male and female with an egg case and a short video with the entire life cycle on a slide.


  • male copepod.bmp
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  • pregnant copepod 2.bmp
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