Your office is awesome! I like your set up, it's very nice. Multiple monitors, and maybe multiple tanks?
Here is some things to consider, I know people say it's been done, etc, etc, where you have HC Cuba and no Co2 and only excel but, that depends on a lot of things. All that healthy and amazing growth was done in a way where the plants had a ton of Co2, now you got the plants relying on carbon from excel.
You either go super slow on growth, where the plants basically grow at a rate that just prevents them from dying, not going to work with that Finnex by the way, or you go Co2.
You can go the slow way, Excel and Co2 from the break down of organic but that way lies damnation. That the most tedious, not fun, barely even a hobby, way. You're not going to maintain that level of growth from Excel.
People who do the slow way, they start it off slow and continue slow. People do the dry start method, start it off fast and continue with that pace (or they try to at least). The last thing I want to happen is for you to spent the next 2 weeks watching it melt.
Pick up a cheap paintball set up, 80 bucks, done. Don't do DIY Co2, that not good enough. Not for that beautiful office and certainly not enough for that beautiful tank.