Algae eating shrimp and fish cannot ever eliminate all algae in a tank. If they ever came close to doing so they would then starve. Otocinclus are interesting fish, and they do eat algae, but I have never been able to see a difference in the tank's appearance due to them. Amano shrimp, on the other hand, can virtually eliminate the clumps of brown algae that litter the substrate in some tanks, so I voted for them. It doesn't take many of those shrimps to make a visible difference, in my experience.