Basically there are only three good options for CO2
. Flourish Excel, DIY CO2
, and Pressurized CO2
. Flourish Excel is a liquid CO2
supplement that works well for small tanks, but would get expensive extremely fast in a tank as large as yours. DIY CO2
has low start up costs, but is a pain to maintain especially in larger tanks. While you could do DIY CO2
on your tank, I would recommend strongly against it. Pressurized CO2
is more expensive to obtain, but is less expensive that the others in the long run and much easier to maintain. It's really the best option especially for larger tanks.
With only running one daylight bulb, I think you'll be okay without CO2
. Just keep an eye on things and your tank will tell you if this isn't the case.