Zcat,
In my zebra tank I have 15 Hengeli Rasboras. Because of their small size they don't bother the zebras and they rarely eat from the bottom.
Along them I have 10 Armano shrimp that do eat from the bottom but don't bother the zebras as well and do a good job in eating algue and left overs.
Finally I have one Dermogynus pumilus that is a surface dweller and therefore never meets a zebra.
This goes very well.