Non Co2/excel Tanks And Water Changes

Hi all

I´ve been reading all your post related with dosing and water changes for non CO2 and Excel tanks. However, it is no quiet clear for me why I should do water changes weekly on Excel tanks and why it is not recommended for non co2 tanks if I use for both the EI dosing.

I understand that if I do a water change in a non Co2 tank, the co2 increases and the plant loses its enzymes. But in the post is recommended for both (excel and non co2) aprox the same dosing: “about 1/8" and 1/32" teaspoon of KNO3 and KH2PO4 respectively once a week or two”. Then:

1. If I use the same EI dosing (above), why should I do water changes in excel tanks and not in non Co2 tank? Will not Both tanks have the same probability of have an accumulation of nutrients? In fact, I would guess that plants in a non co2 tank will grow slower and then, less nutrients are consumed.
2. If I dose excel in a daily basis, (2x the recommended dose) what would happened if I do not add excel some days a week? is It mandatory to be steady with this excel dosing.

Regards