Coincidentally, a well known gesneriad grower just posted this on Gesneriphiles:
Underwater Design - Best Flowers
•Saintpaulia
•Aeschynanathus
•Columnea esp. linearifolia
•Nematanthus (will separate from calyx; glue corolla separately
Underwater Design – Worst Flowers
•Streptocarpus
•Primulina