Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
I think that any differences in when the plants take in the ferts and how they are broken down in the tank is offset by the 'user error' factor.
Best info: Dose when you can, on whatever schedule you will be most reliable.
If you have time in the mornings, and can (pretty much) always dose then, do that.
If your mornings are often rushed, and trying to dose then will result in hit or miss sort of dosing, then dose in the evenings.