Hi,
Well, yes mate, if you think it looks better then that's the bottom line, definitely go for it. Your question was why others don't use the box method and why you haven't seen anyone else using it. That's the query I was addressing.
CO2 affects the pH of the tank radically. Of this there is little doubt, however neither you plants nor your fish care about fluctuating water pH. Adding too much CO2 has a negative effect on fish due to the pH drop in their bloodstream, not due to the pH of the water. This is called blood acidosis and it has a lethal impact on fauna. The pH of the water column though has no effect on the pH of the bloodstream. In order to monitor the CO2 content it's better to use a dropchecker filled with 4 dkh water, as well as to monitor the behavior of the fish.
This is a crucial misconception and this is why many worry needlessly about buffering and so forth. It's completely irrelevant. Fauna have mechanisms to prevent H+ ions from penetrating the blood stream, however CO2 must be ejected from the blodstream in the same way we exhale. This happens by osmotic pressure so if the CO2 concentration of the water is lower than the concentration of the blood then CO2 will travel from the blood to the water. If the concentration of the water is too high then the external CO2 osmotic pressure is higher in the water and therefore CO2 cannot escape from the blood. The bloodstream therefore gets flooded with CO2 from the water and the Carbonic acid formed in the blood wreaks havoc on nervous system, liver and other systems.
If low pH in the water column was a problem then all the South and Central American fish would perish because these water are extremely acidic. Not only that but the acidity varies wildly from one body of water to the next, and from one day to the next due to rain and taniic acid leaching into the water from the leaf litter and sediment. In fact, many species use the extreme pH fluctuation as a trigger for breeding. So there is no way low pH, pH crash or fluctuating pH is problematic. My suggestion is to forget about water ph and think more about CO2 concentrations.
If you are having surface scum it's more an indication of poor CO2 and/or poor nutrition. Proper nutrition combined with adequate surface agitation, regular fluffing of the plants to dislodge detritus and proper flow eliminates this condition.
Cheers,