Cool thanks for the updated pic
2 sides of this that I want to try and work out, firstly lets chat about the fish.
With a Co2 injected tank you have to be super careful with the number of fish (especially with big fish like the angels) as you can suffocate them if you inject too much or if you dont have enough plants to use the Co2 and convert it to oxygen.
Using aqua soil and Co2 can also lead to fluctuating hardness and ph. Its also good to know what these factors are so you can get the right fish in the tank too. I think you mainly have softwater fish from what I can see but if you can give us a list or species and numbers that would be great
Secondly, with the scape I think you need a lot more plants, especially if you want to use Co2 as you don't have enough at the moment to convert Co2 to o2 (if you are injecting the amount of bubbles per second I'd expect here). Do you know the names of the plants you have? From your pictures I can see Anacharis, Red Camboba (I think?), Ludwigia, maybe some Rotala Rotundifolia at the front right? And I think the carpeting plant you have at the front is Monte Carlo? Most of these plants would be fine if you turned off the Co2, the Monte Carlo might fade but I'd be tempted to have a think about doing this unless you can add a lot more plants to the tank.
In terms of if you get the chance to replant - think of plants in terms of background, midground and foreground. Backgrounds are your big plants like Swords, Lace Plants, Java Fern, Vallisnera and stem plants like Hygrophilla, Hydrocotyle and Limnophilla species. Mid ground are some of the smaller stem plants and large to medium cryptocorynes as well as some of the epiphites like Anubias and Bucephalandra. The foregrounds are small crypts and carpeting plants like monte carlo, hair grass and Lilaeopsis or Helanthium.
With the way you have the sand and the soil you may also run into trouble over time as they will blend together, to keep them separate you need to make a wall with your hardscape otherwise the heavier of the two grains will eventually merge into the other due to circulation and gravity.
I'm sure you are already all over youtube
but have a look at this video and how he has set the tank up. From how hes done the substrate, the amount and style of hardscape hes done and then how he has positioned the plants (hes used some of the same species here that you have).
Hope this helps, sorry if I'm a bit negative but just got to be serious when using Co2 as it takes a while to get the hang of and can be dangerous if you don't do it quite right.
Wills