The diet of P. axelrodi consists of very small crustaceans, mesofauna, eggs, algae, detritus, and some other types of prey. Most types of small crustaceans eaten are cladocera (small, spherical moinids, daphnids, and macrothricids), as well as some copepods (benthonic Harpacticidae). Rotifera and Thecamoebae are included in the mesofauna that cardinal tetras eat. The types of algae that they eat include unicellular diatoms (Navicularia and Pinnularia), and some green algae (Chlamydomonas, Conjugatophyta, and Volvocaceae). Cardinal tetras sometimes feed on dead fish, eating the detritus of their muscular, proteinous, and membraneous tissues. Paracheirodon axelrodi individuals may also eat ants, Diptera larvae or pupae, mites, newly hatched shrimp, fungus, pieces of fruit, and fish larvae.
Animal Foods: eggs; carrion ; insects; terrestrial non-insect arthropods; aquatic or marine worms; aquatic crustaceans; zooplankton
Plant Foods: fruit; phytoplankton
Other Foods: fungus; detritus ; microbes
Primary Diet: carnivore (Eats non-insect arthropods); planktivore