Hey NCGUY, I'd like to add in my opinion here. It really depends on what plants you have in your tank, your lighting, and your fert regiment.
For instance, I have a 29 gallon with 2 T5HO bulbs, and a Finnex Planted + 24/7. I dose EI method and have a lot of demanding, fast growing plants. Because I have high lighting, and lots of nutrients in the tank I must supplement the plants with CO2.
What plants are you trying to grow and what lighting are you using?