Otocinclus-oto
they prefer soft algae including diatom-brown algae..I have never seen them eat beard algae, hair algae, green slime algae(cyano bacter)
if you are lwo on algae, oto's have a tendecy to eat a lot of algae)
you can substitute: algae wafer, , cucumber, zuccini(blanched) other squashes.
keep in mind if they have never eaten this they will need to get accustomed to it..I have had oto's refuse everything except algae..
they are terrific catfish but can be difficult to keep.