The tank is looking very good.
This thread reminds me of my 28 gallon tank. I started with low light, then added more light and DIY CO2
like you have.
My next move was to get rid of my HOB
filter and replace it with a cannister. I then replaced the substrate with a more natural looking one. Next was a better way of dissolving the CO2
and then onto a pressurized CO2
system. (I can see your future)