Ewww I hate the term imbalance used in association of planted aquaria.
I tend to explain a planted tank to you in a car being chased by the police!!! explanation
police car = plants(particularly the light they require)
air drawn into your car engine = CO2
Fuel into your engine = Ferts
Finally your foot on the throttle/accelerator = lighting
the police car is at a certain speed / your plants require a certain minimum of light
to keep in front of the police car you must have air and fuel into your engine and must hold the throttle at a certain position to maintain speed / for your plants to grow you must have co2 and ferts to supply the plants the speed they use these is governed by the amount of light
if you accelerate too hard put your foot down you will use more air and fuel / if you have more light you will need more co2 and ferts
if you run out of fuel police catch you / if you run out of ferts algae grows
if you run low on air you slow down the police catch you / if you run low on co2 algae grows
the controlling force is the throttle/accelerator / the controlling force is the lighting (the limiting factor)
plenty of air and fuel will not cause the police to catch you / plenty of ferts and co2 does not cause algae
I am sure you get the idea.
Happy fishkeeping