I chose an Otocinclus. This fish attaches itself to the side of the tank and eats the algae. Occasionally it swims around to another location, but most of its time is attached to the tank.
I also cleaned the tank this week. After moving one of the decorations, I caught a glimpse of a teeny, tiny crayfish. It is still alive. Cool. Hopefully it makes it. Right now the crayfish is about a centimetre long and dark like the rocks in the tank. When it doesn’t move, you can’t tell it is a living creature.