Thanks Naman,
That was precisely the input I wanted to see

ADA AS adds a measure of buffering, so you can have even a wider range, and can run things leaner if you chose.

Rather than using PPS nutrients to slow growth/CO2 demand, both ADA and myself prefer light.

PMDD also limited PO4 to the point is reduced CO2 demand as well.
So 15ppm was fine.
However, they used 1.5-2 w/gal max back then also using plain old T12 FL light.
Some seem to overlook this, almost on purpose.

This makes far more practical sense as well, cost less, adds less heat, uses less initial cost, and drives CO2 uptake.

When plants are CO2 limited due to high light, algae are not.
So if you are interested in less algae and better plant growth, it makes far more sense to use less light, then you need less CO2 and less nutrient demand.

That is why non CO2 methods work, less light= less CO2= less nutrient demands and is why you do not need to ferts to such a tank, fish waste alone can easily supply the plant demands.

Plants also have a wide range of parameters they can grow in before really taking a beating.

The ADA As works very well with non CO2 methods as well BTW.