I have the same light over my 29 and I use flourish about 1 time a week. what are you growing ? different plants need different requirements. I have low light and medium plants and no algae and no CO2 and I do not bother with ferts except flourish
Flourish products can get expensive, even with only having a 30gal.
Excel would be good to use in conjunction with a DIY C02 rig. Otherwise you could burn through a bottle in no time.