You can take another approach which is start off lean and gradually increase until you reach optimal plant growth. This is the approach I took, but as stated above, these fert regimes are not written in stone and you should change them as you see fit. For example, I took the basic PPS Pro formula and increased it to fit my tank conditions. So right now I am dosing the basic PPS Pro dose but I found that I also need to add more phosphate to keep GSA in check.
I test for nitrate and phosphate and with my feeding and fert regimen I keep nitrates around 20-35 ppm and phosphate around 3 ppm. I change 1/3 water in my tank every week or two. I generally test about every 2 weeks but things have been pretty stable for months now.
I think the advantage of EI is that you start off without limiting plant growth and taper down/up as needed whereas the way I went I was/am probably limiting nutrients in some way which limits plant growth. Either way, over time with the proper adjustments, you should end up in the same place.
You start off with stunted nutrient starved plants, better to start high at a non limiting level, then reduce. This way you have a reference of what non limiting nutrient dosing looks like, you do not have that reference with PMDD which all pps pro really is.
With EI, you start with a reference (PMDD/PPS you do not start with any reference), then taper down slowly till you hit a point where there's a response.
Both "methods" add the same thing, so the only difference is at what concentration. EI is just an upper bound(non limiting) form of PMDD and assumes that PO4 is NOT a limiting nutrients for algae control.
But with more nutrients, obviously..........we increase the CO2 as well..........and the light starts the CO2 demand, so knowing the lighting is critical since all growth starts there.
You cannot take CO2 out and make it just 15ppm for all tanks cause it feels good or it worked a few times for you, this does NOT work. I also have many issues measuring CO2 critically, and 99.99% of hobbyists do as well, they assume it's good, but often it's not.
I run 45-60ppm in many tanks, others will run to 60-70ppm etc.
Depends on the plant species involved also, not all plants have the same CO2 demand and constants for uptake over a range of light intensities.
In other words, we cannot piece meal CO2 and light, they are the main drivers of nutrients and uptake.
Also, GSA is not a PO4 issues with EI. I modify this and add even more PO4. Likewise PMDD can be modified and more PO4 is added(generally 2-5ppm ranges) now suddenly PMDD is exactly PPS pro without any citations or credit given to PMDD which predated PPS by 8 years curiously and everyone was well aware of.
Unless you have non limiting nutrients, you cannot also have independence with CO2 or with light. So if you are only dosing barely enough CO2 for a strongly limited PO4 system, adding more PO4 will lead to strong CO2 deficiencies. This is tougher to balance and slows growth with more management issues, than say, simply using something far more stable, like....... less light. All growth starts with light, then goes to CO2.........lastly......nutrients.
So management, slowing things down, should be best done with that in mind, not 100% nutrients. No dosing should be that critical or micromanaged.
It's just not practical.
PPS classic attempted to test the snot out of everything and while it's relatively easy for myself to achieve this, for many, it's a daunting task and a hard sell. So PPS devolved to PMDD basically and made it simpler, but when it did that..........it took credit for someone else's prior work and ended up being the same thing. Any/every method needs to be simple and easy for the user. But many try to play this game with less is better somehow, playing upon the old Myths, but plants grow best when the ferts/CO2 are non limiting. Liebig clearly stated this law in agriculture 170 years ago. No way around it.
Our goal is a simple easy way to manage gardening/scaping for horticulture.
So the goal is really to grow plants well. That's what I do.