Hello,

The addition of the MH light spectrum is still benefitial to the growth of the plants. Though a hortilux bulb does cover more of the spectrum than a regular HPS bulb, it does not cover the full spectrum that a MH bulb does, it is best to run both in my personal opinion.

I agree with Zandor though, if you only have the funds for one light system then I would go with the HPS along with the hortilux bulb.

Take care all

Peace