[plantbrain]

2 tanks I have never done a water change yet. Been over a year.
Other CO2 enriched tanks generally weekly. 2x a week if I want to whip it into shape.

I do larger changes, about 60-75%.

Regards,

Tom Barr

 

[plantbrain]

Near as I can tell,
The reason for fewer water changes as a function of lower light/CO2, is one based on rate.

At lower growth rates, the tank(bacteria and plants) have more time to reminerlized these organic fractions and small low residual lecvels are still able to supply the plants with their growth needs that a greatly slowed by less light/CO2 etc.

As you increase the growth rate of the tank, you need more and more inorganic sources for nutrients.

Water changes remove the organic fraction and also organic accreation or mulm etc. Algae like the organic fraction at high light.

At low light and non CO2 cases, the algae have less energy to drive this process.

Regards,
Tom Barr