Often classified as algae, Euglena is a freshwater flagellate. It is a single-celled organism with over 1,000 different species. Toxic Euglena algae blooms have been known to cause fish kills. It can also change colors depending on light intensity. Within minutes it can change from a green color to a red bloom. Euglena has a strong protein pellicle increasing its defenses to certain chemicals. It has the ability to cover entire ponds, which can be, extremely problematic.
