Wouldn't #3 be a flagellate? Being that is has 2 flagella?In the videos:
#1 is probably a copepodite, but could be a rotifer
#2 Is similar to Vorticella - usually found in freshwater, but sometimes marine
#3 possible ciliate (Euplotes?)
#4 Copepodite? Larval copepod.
#5 IDK
Jay