You mean HPS instead of MH? No it wont hurt. The difference is that MH has more Blue spectrum light that promotes vegetative growth, while HPS has more Red spectrum which promotes flowering growth more.

So for the 1-3 days, it'll be completely negligible.
MisterE Reviewed by MisterE on . Oh No, I may have messed up! Rut-row...hope this isn't a problem. My second ballast is an HPS only, and I thought I got the switchable, however I never opened it until it was needed. One ballast is switch-able and one isn't... would it harm the plants if I transplant, and have half of them under HPS instead of HID? Then once they adjust to the transplant 1-3 days later, switch them to 12. 12 Any other ideas? Sorry for being such a newbie here! Right now I have about 35 clones under a MH lamp, and I need to transplant Rating: 5