You'd be looking at upper levels, could go with some rosy red minnows (6-8) and they'd stand out among your danios and not take up territory among the bottom dwellers.
Some other contenders:
Red eye tetras (6-8)
Bloodfin tetras (8-10)
Skirt tetras (6-8)
They'd play well with danios and are all from cooler areas of south american so will do great in low 70s temperatures, but you'd only be able to look at schoolers.
@GaryE would any Gardneri type killifish work in a 55 gallon with zebra danios, BN pleco, and garra or are they lower level fish/warmer water fish?
Some other contenders:
Red eye tetras (6-8)
Bloodfin tetras (8-10)
Skirt tetras (6-8)
They'd play well with danios and are all from cooler areas of south american so will do great in low 70s temperatures, but you'd only be able to look at schoolers.
@GaryE would any Gardneri type killifish work in a 55 gallon with zebra danios, BN pleco, and garra or are they lower level fish/warmer water fish?