Hi Lawrence,

Welcome to this forum! I manage to set up a 4 ft tank with the help from forumers here. I'm sure you'll be successful too with the help from the forumers here.

Can you let us know how dense and what plants that you hv there in your tank? As a beginer, I would suggest the following:-

GH ~ 3 - 6 dH
KH ~ 3 - 4 dH
pH ~ 6.6 - 6.8

With DIY CO2, I guess you may have difficulty to sustain a constant pH value. I would strongly suggest you try Flourish Excel as additional Carbon supplement in addition to your DIY CO2. This will ensure that your tank is not C limited.

Need more information b4 I can give further suggestion on fert dosing.
How about the substrate? Any fert?

rgds
Yean Chon