Bru honestly why would you want a PAR meter? Not worth it imo, rather spend that on a good PH meter or a humidity or temp controller. Also with regards to running it 20/4 opposed to 18/6, plants use the darkness to grow, so yes even tho more light is good, the balance of 18/6 is great because they have 6 hours to do their thing. Sent from my G3312 using Tapatalk