I mean if I decide to do EI dosing I'll have to do 50% weekly changes.
No, there's never been have to about EI, 50% is simply a starting point that's arbitrary. It is a myth to suggest EI demands or requires this.
It will raise your error factor........but that might not be an issue.
I do 1x a month on two of my tanks for example.
Plants love water changes, you cannot over do them.
ADG, Jeff Senske etc, Amano, Myself, we suggest large weekly water changes, and this is a wide range of folks from independent lines that all came to this conclusion.
It is not bad advice in the least.
Sediment ferts are logn term and easy, they provide a back up if you forget to dose or want to dose less for some reason........say you believe in the myth that less ppm in the water = less algae. You have an option.
Sediment vs water column should NOT be viewed as "either... or".
Rather, it should be view as complementary and synegistic
. One supplyes the roots, the other the leaves, this takes the avantages of each and gets rid of the disadvantages of each as well.
A better study from Madsen and Cerdergreen looks at 4 species of plants in a nutrient rich stream...they even cut off the roots, and the shoots still had the same rates of growth.
Pretty much states what all researchers already know: aquatic plants are opportunistic, they will nab nutrients where ever they are, the same is true when given the opportunity, to terrestrial land plants via fertigation......
Sediments offer another source.........of nutrients. But this does not mean osmocoat and anythign else you put into there does not leach and crequire water change sif the ferts build up......ADA aqua soil neeeds frequent water changes initially till the leaching stops.
Far more than EI suggest at 50% weekly.
Still, it's better to do a water change than not.
Once you get the hang of things, then you can progressively reduce the ferts and then you can start to reduce the water changes, mostly the frequency.......
This I've long detailed if you wish to do few water changes and view them as hidious chore.
Making the water change easy and you still need to trim and garden some either way, I do the water change while I clean and other routine things to the tank, even with 480 Gal worth of tank, I spend less than 1.5 hours a week and keep the tanks looking in pretty decent shape.
Some folks sell sediment ferts as some way to entirely avoid water changes, while to some degree this can be true........you do get better growth by doing both and the short and the long term management is easier.
I like to do them personally and the tank looks better. If you honestly hatre water changes, then do non CO2.
If you hate water changes but are not willing to give up CO2..then use low light, since that is what determines CO2 and nutrient uptake.
In otherwords, there's no single silver bullet to avoud water changes, you need to consider the aquarium holstically and start where growth starts, then go down one by one to achieve the best management practice for your goal.
Suggesting sediment ferts will solve all algae and dosing issues is rubbish however. But that is how many like to sell it off as.....