Ok, I think I need to clarify:
I am NOT looking to eliminate water changes. I am looking to reduce their frequency.
I should also note the tank is low-medium light, daily glut, no CO2 injection, modest dosing of P,K, and micros based on EI low-light profiles.
Under this type of routine, I typically suggest 1/4 to 1/3 EI, not 1/2.
Water changes typically run once a month.
Once a month say 50% is better than 2x a month of 20% regarding any build up of any nutrients.
And it's nearly 2x less work. You should harm no buckets in the process, if you use buckets, you are doing the water change the wrong way. Takes but 5 more minutes just once and you are done.
Dosing, maybe 2x a week. Some go 1x a week with this method.
Plant species: chose a few fast growers , but mostly slower growers.
Keep the fast growers well trimmed. Glut at 5 mls per 10 Gal of tank daily.
Good current, clean filters every other week or once a month as needed.
Adding water to counter evaporation will be an issue. Then a bucket might be used.
A garden hose with a PVC J hook can drain and refill the water once a month.
One end goes outside to the grass or landscaping plants, then after draining to the desired level, you take the same drain end and hook to the shower head with a 1/2 to garden hose connector(they have these at Home Depot)
Once you established your desired goal/method, then it's much easier to give you or anyone a simple routine. Plant tanks run the gambit from low light/no CO2/Glut etc, to high light and lots of CO2, and everything in between. No one method will suit all tanks.
If you are not adding KNO3, then I would also add GH booster once a week, maybe add around 1/2 degree of GH. It's got some K2SO4 in it, about 50% by weight.
50% water change makes the math for dosing EASY also.
Assuming the tap water is zero ppm, the max build up due to dosing will be no more than 2x the dosing you did between the 50% water change.
Say you dosed 10 ppm over 1 month of NO3 as KNO3, the maximum possible build up would 20 ppm in the aquarium with a monthly 50% water change. Now, you no longer need to test or measure, you know you are within the 20ppm or less upper range. All you need to worry about is dosing too little.
This way you can further reduce the labor(fewer, but larger water changes, no testing).
If you'd like to model the outcomes of EI dosing versus time and build up, see here:
Note, if you go under optional, you can use known uptakes and even fish food % by weight of N and then use a 90% wasted N factor for the N produced from fish waste.
Also note: EI's 50% water change is entirely arbitrary, it's a simple method and the math is easier for most using 50% weekly.
It really depends on how much build up potential excess you are willing to accept.
Same with the frequency of water changes.
Generally, you maximize the dilution to labor ratio by doing larger % water changes, vs many smaller ones more frequently.
Once you start a water change, may as well go big if you have a freshwater tank(or a Marine tank for that matter).
Does not take that much longer to do 20% vs 50% once you drag the stuff out and start the job.