Dr Engelbert Buxbaum wrote in message ...

Algal growth is usually the result of wrong conditions in the tank: too
little or too much light, high content of phosphorus and nitrate. In a
properly maintained tank growth is limited and can be controlled with
catfish or snails, if that is desired.

In planted tanks:
For green water cultures, you cannot start them using PO4 or NO3. Even
at 75ppm of NO3 and 2-3ppm of PO4, the alga will not bloom.

If you add a little trace amount of NH4 or urea combined with high
light, then you will get Green water.
Once the culture has been started, then extra CO2, PO4, NO3 will/can
be used after the NH4 is gone and can maintain the cultures at
extremely low levels(beyond any hobby test kit ranges eg Lamott or
Hach).
You will slowly kill your plants long before you limit green water.

Regards,
Tom Barr