Dinoflagellates Zooplankton – Part 1

Dinoflagellates have an infamous reputation for aquarium hobbyists and there is a good reason why. Dino’s are essentially a type of algae that grow and reproduce in your tank and some species are even parasites on zooplankton, fish or other organisms. So in this two-part blog series, we are going to take you through the following:

Part 1: More information on dinoflagellates zooplankton & how to identify them in your tank

Part 2: How to avoid getting dinoflagellates zooplankton in your tank and how to get rid of them.

More about dinoflagellates:

Some dinoflagellates produce resting stages, called dinoflagellate cysts or dinocysts, as part of their lifecycles.

There are approximately 4,500 species of dinoflagellates. Here are the three main types of dinoflagellates:

  1. Non-photosynthetic – feed on diatoms and other dino’s
  2. Photosynthetic – feed on light
  3. Mixotrophic – feed on light, microalgae & diatoms

Non-photosynthetic species of dinoflagellates feed on diatoms or other protists (including other dinoflagellates); Noctiluca is large enough to eat zooplankton and fish eggs. Some species are parasites on algae, zooplankton, fish or other organisms.

At least 10% of all dinoflagellates, and in temperate areas as much as 28%, are resting cyst producers (Persson et al. 2000). Sexual reproduction is thought to be essential for seasonal survival of these species, although asexual resting cysts are also known in Scrippsiella hangoei (Kremp and Parrow 2006).

The different sexual and asexual routes can be summarized as shown in the following diagram:

Fig. 1.Dinoflagellate life cycle (modified after Walker et al.1984).


Are dinoflagellates toxic?

Some but not all red tides are toxic. In toxic red tides, the dinoflagellates produce a chemical that acts as a neurotoxin in other animals. Another toxin that accumulates in shellfish is brevetoxin, produced by the dinoflagellate Karenia brevis. A toxin produced by the dinoflagellate Dinophysis causes diarrhetic shellfish poisoning (DSP), which results in digestive upset but which is not fatal. Ciguatera is another form of dinoflagellate toxicity in tropical areas caused by eating fish contaminated by toxins of the dinoflagellate Gambierdiscus toxicus.


Indications that you have dinoflagellates in your tank.

  • They can stretch out and grow bubbles.
  • They can be a rusty brown colour, yellow, or rusty orange.
  • Parts of the sand bed can look a little rusty.
  • They appear to be brownish strands and can create air bubbles.

We hope you now have a good understanding on dinoflagellates and how to identify these organisms in your tank. Stay tuned for next weeks blog ‘Dinoflagellates – Part 2’ on how to avoid getting dino’s in your tank and how to get rid of them when they are in your tank.