Raymond is giving you advice and sending you to a web site dedicated to high tech tanks. Yes it works well for High tech, but thats not what you say you have. Low tech equals little or seldom doing water changes.
It might be even more thoughtful if when someone says your source is for high tech, that they might look at it and see if they are making
an incorrect statement first. Less chance of them looking bad that way.
If you will look at the list...there is a section for non-CO2 tanks. The last time I checked...non-CO2 was/is low tech. Long as you don't have high lights.
Zorfox has good info. I just think that IF your tank has anything like a stocking level of more than 80% then once a
month is cutting it a bit too close for me with water changes. Too much chance of a buildup of toxic chemicals. I didn't have any way to calculate the amounts in liquids. I also thank Zorfox for doing it for you as you do have them and even if you decide to
change to dry ferts later you will likely use up the liquids first as I am/w Flourish Comprehensive that I had before I
went to the dry ferts. No sense in wasting them so I won't get the Micro's in dry till I run out of the Flourish C.
I use Excel now but hope to eliminate it later after my plants have filled out the tank some more.
What is really funny(to me at least) is that most who have injected CO2 say that Excel doesn't qualify as CO2. Please spare me
from that debate. I use it because my plants seem fuller than when I didn't. Just better all around in general.
Don't notice any change in the growth rate though. We'll see when I decide to stop it.
There is a section on the fert calculator which gives "EI low light /weekly" doses. I use less than those, but basicly the same
list for ferts as the regular EI.