Silver Tetra

Silver tetra Gymnocorymbus thayeri
Silver tetra Ctenobrycon spilurus
Silver tetra Micralestes acutidens
Silvertip tetra Hasemania melanura
Silvertip tetra Hasemania nana
Silver-tipped tetra Hasemania nana
Splash tetra Copella arnoldi ...

Scissortail tetras and silver tetras are also nice additions. I've had good luck with zebra danios as well in discus warm waters.

These include the Moenkhausia Tetras (Glass Tetra, Red-eyed Tetra, and Diamond Tetra), the Serpae Tetra, Slender Hemiodus, Silver Tetra, and the Blind Cave Tetra.

See also: Fish, Silver