They(non CO2) start well out of the gate, you can add nutrients to keep them going though, start dosing SeaChem Eq, KNO3, KH2PO4 etc.

It's amazing they do grow as fast as they do when you add the right nutrients once they begin to hit the lull.

The same thing use to ocurr with CO2 methods till folks started adding PO4...

Regards,
Tom Barr