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Water fleas (Cladocera)

Taxonomic group

Order: Cladocera

Diagnostic features

Cladocerans are often referred to as water fleas and they are commonly used in the aquarium trade as fish food. They are small (less than 5mm) crustaceans, most of which can swim in a jerking motion using their antennae. Most of the body is enclosed within a transparrent covering (the “carapace”).

Typical habitats

Cladocerans are primarily inhabitants of still waters, or rivers downstream of lake/pond outlets. They can be common in water troughs, and some species can be abundant in sewage treatment ponds.


They are filter feeders (feeding on plankton) but some can also scrape biofilms off submerged surfaces.

Indicator value

  • Hard bottom: 5
  • Soft bottom: 0.7

The tolerance values (ranging from 0 to 10) give an indication of which are the sensitive taxa (values of 8 or more) and which are the tolerant taxa (values of 3 or less). For more information see: Indicator species

Cladocerans are indicative of pond-like habitats, possibly upstream of your sampling site. They have moderate to low tolerance values of 5 (hard bottom sites) and 0.7 (soft bottom sites).