Well fed fish and well fed plants is a common sense approach to keeping aquarium livestock and plants.
Plants are not merely about the nutrients, CO2 is a nutrient and the largest one really. Light is fairly stable and few folks are ever too low when using CO2. Most are too high with light intensity.
These both affect the results for nutrients/rates etc.
No dosing routine will match all tanks as their rates are different, but we do know the upper bounds/rates. From there, you reduce down (or not, these rates will do no harm, see below).
Starting low and bring it up higher till no more positive effect is noted is much harder, and takes longer. Why? The plants are already starved/limited for nutrients. It takes longer for them to adjust that if they where fat and happy to begin with.
You need to start with a good plant reference state, not a limited plant.
Same for testing algae and analyzing why you have algae.
You need a reference tank(one that's doing well and is nice and healthy), testing a 1/2 dead plant, algae covered, stunted, limited....is hardly a good comparative method to gauge and discuss a treatment.
Still, many aquarist seem to think that it is rational to assume they can "test" something without any control and a loused up tank.
You must have some reference to compare by.
You can look to research for plant nutrients. A basic tool is using Hoagland's modified solution and then DI water for nutrient solution references, one complete and non limiting (Hoagland's), the other, devoid of any nutrients(DI water).
Any sediment or nutrient combination in between will fall somewhere between these two. In the case of salt and other toxicants, it will also do worse than the DI water, but as far nutrients alone, the DI water will have the least.
Now you have a relative measure for any nutrient in between these two concentrations.
EI is pretty much like Hoagland's modified and without the NH4.
Gerloff and Kromboltz(who comes to the AGA conventions, still posted on the APD etc) decades ago used a 1/5th Hoaglands for aquatic plants, which, is about what EI's range is.
http://allhydroponics.blogspot.com/2...ydroponic.html
Now at :
N 210 ppm
K 235 ppm
Ca 200 ppm
P 31 ppm
S 64 ppm
Mg 48 ppm
B 0.5 ppm
Fe 1 to 5 ppm
Mn 0.5 ppm
Zn 0.05 ppm
Cu 0.02 ppm
Mo 0.01 ppm
These are pretty high, yet some clowns claim that 20ppm of NO3 causes plants to melt
Such solutions above are what is used for commercial growers of aquatic plants(95% of all aquatics)! Not to mention most other crops. This information is widely available. Many aquarist seem more than willing to **actively** ignore it.
Regards,
Tom Barr