No light at night. Light prevents deep rest (for humans also, by the way- night lights aren't good for us- even a little light is not good for optimal sleep).
Also no heat at night of any kind. Veileds can easily go down to 50 at night- I let them go into the low 40s even with no problems. New hatched babies down to 50 is not a problem. Reduced temperatures lower the metabolism and provide a deeper rest state.