Best fertilizer combination for a 200 L planted coldwater aquarium?

Hi,

I currently have a heavily planted 200 L goldfish aquarium. My plants currently consist of mainly java ferns, anubias, vallisneria, elodea crispa, java moss, and a couple amazon swords.

I have two Hagen Aqua Glo tube lights, which I leave on for about 8 hours a day. I have been dosing 2 x a week with Nutrafin Plant Gro. The plants are all doing well, but I would like to see more growth. I do have a very well behaved goldfish, so I do not have the problem of it eating or uprooting the plants.

I have been investigating putting in a CO2 system, even though Goldfish are a good source of fertilization, I only have one small one in my tank so I don’t believe that is enough to make up for no CO2..

I read about Seachems Flourish Excel, which is a liquid CO2. Can any of you recommend whether I should use that as well as Nutrafin Plant Gro, or whether the Flourish Excel is worth using? Thanks!