I agree...EI is a lot less rigid than PMDD seems to be.
At the time, folks where all doing PMDD, I just happen to have had high PO4 in the tap.
I was initially turned off by all the "chem speak", thought I needed to know more than I really did, knew folks simply would not bother to test much.
Most of it was human social habits, not science so much. Basically, what makes a planted tank easier, easiest to manage with the least amount of back ground and assumptions.
1. Folks know how to use a teaspoon to cook, bake cookies and what not.
2. They have to know how to do a water change if they own an aquarium, most are fine with this.
3. While we can use math to predict the outcomes, the hobbyist do not need to know it to estimate, they can simply use a a simple easy target, say 50% weekly water changes.
4. This takes the least amount of time to explain.
It also rules out testing issues such as calibration and reference standards. Folks have enough issue testing, let alone doing these extra but needed steps. Who got into this hobby to test? None I've ever met.
EI was more a response to human issues, than a better method itself.
I had suggested using high grade test kits and calibrated references.
Then dose + test+ do water changes.
Later, I included sediment rich source of nutrients as well.
Adds a back up source of nutrients and allows the user more wiggle room.
Some go lean and rely more on the sediment, and dose less to the water column, others keep dosing rich and get a longer life out of the sediments.
Both have the same results, there's no significant difference.
I use large water changes as a chance to clean my tank, amplify growth(tank's always pearl like crazy if you do the water change in the morning for the rest of the day light cycle), clean out the filter, prune without sloshing water, or stick my head under water, makes cleaning, pruning and all the other scaping aspects and maintenance issues much easier. I use a simple PCV U shaped hanger for a drain and refill, with a screened Tee so the fish/shrimps do not get siphoned off or water blast the gravel etc away. Those 3/4" overflow screens they use on bulk heads are very good for this.
Then you get a garden hose adapter for the shower head and the pvc, now you can fill/drain very easily and while it drains, fills, you do the other stuff above.
Easy, takes maybe 45 minutes to do a 70% water change and prune, cleaning, etc, everything, for a 180 Gal tank. Takes me 2 hours a week to do 5 tanks totaling 440 Gallons. I water the landscaping with the waste water.
So I do not need nor use an irrigation system for the yard.
This typically used about 200 Gallons 2-3x a week. I add no chlorinate water to the yard, so the bacteria and other organic critters provide a much better cycling and health to the plants there. Once done draining, I switch the other end to the shower and fill.
Goes pretty quick.
If you have your own home and large tank, you might simply have a permanent hard plumbed drain and refill. This makes it even easier, turn a valve to drain, turn another to fill. Soem folks use float siwtches and solenoids to automatically do the water changes, and if you have a controller/ethernet, this can even be done via your phone.
If you use lower light+ slowly and progressively reduce the dosing from high to lower.........then you can reduce the dosign and the water change frequency by simply watching till you notice a negative response from the plants, then bump the dosing back up to the next highest level.
You cannot see this if the plants are limited and struggling to begin with.
It might be CO2 or some other factor.
So it's best to start with a fat plump plant and then reduce it from there if you want to add "just enough". Lower light drives uptake and growth slower for both CO2/nutrients. So you have more wiggle room and better management. Therefore you can reduce the water change frequency down...if that's your goal etc. If you really want to reduce things down even more..then perhaps go non CO2, and use sediment ferts (All cases for that matter) and maybe Excel etc, then 1x a month for Excel is common for water changes, or not at all for non CO2.
No one method will do all of the goals folks have, but lower light will make most of them much easier.
That is one of the more universal issues.
Dosing nutrients is the easy part.
Some make it complicated, but after a couple of weeks, it's old hat.
Folks test etc also, you can still do that, but do it right and use good equipment and reference solutions. Most stop after few times anyway. So it's not something folks really do much over time, typically only if they have an issue, then it's not adding enough perhaps or nothing to do with nutrients at all.
Regards,
Tom Barr