I suggest you take a step back and think this through.
First, as others have mentioned, with the current plant species you do not need added CO2. I grow these plants fine, and have for over 20 years, and never added CO2.
Second thing is that if you do add diffused CO2 you will need to up your light, as what you now have is insufficient to balance. And you will also need to add the other nutrients. One can have a "planted" tank using different methods, from low-tech or natural up to high-tech, but with whichever method there must be a balance between light (intensity) and the 17 nutrients (of which carbon is just one). Plants grow via photosynthesis, and they will photosynthesize to the full provided everything they require is available. As soon as any requirement is lacking, photosynthesis slows and may stop completely--what we call the law of minimum. Algae then takes advantage.
Third point is on the liquid carbon supplements. You mention Excel and copper; there is no copper in Excel. Excel is water and gluteraldehyde (Seachem call it something else, but the product fact sheet gives this chemical). I personally would never put this toxic chemical in a tank with fish or invertebrates. It will kill some plants outright (Vallisneria for one) even at the recommended dose. At higher doses it will kill plants, bacteria and fish. This chemical is used in hospitals to disinfect, in embalming fluid to kill bacteria, and in antifreeze. The fact sheet from the government warms of not inhaling and burns to the skin. Now, I know that some aquarists do use this product, and have no issues. Fine. But I do not recommend adding something like this to an aquarium when it is not necessary. This is just my view, to set out the facts, not to get into another argument over Excel. Each has to decide what does or doesn't go into their aquarium.
Byron.
That picture of yours always throws me, and I forget you are a female. Haha!
