If you can keep the temps low enough (30-55F), then light is not necessary. Cacti become dormant during the winter, they are not actively photosynthesizing, light is not needed.

I never had Melocactus, Discocactus or some of the other types that come from areas where there is year-round warmth, so I can't speak from experience regarding those.

As far as I'm concerned, all terrestrial species from the SW USA, Mexico, and the globular S Americans (Lobivia, Echinopsis, Rebutia, Parodia, Notocactus, Copiapoa, etc) will respond equally well to cold and dark. I've been doing this for over 10 years easily.

But...if you can't keep it cold, they are still dormant, and plain old fluorescent lights are adequate. Before I began storing mine in the cold and dark, I kept them warmer and under lights. Make sure there is good ventilation because with more warmth there are more pests.

x