I would not put too much thought into Amano's measurements. He does not strike me as a plant physiologist. Wim mentioned that when we talked to him in the past. You can tell from his answers.
When I see data that is as consistent as those measurements, I know something is up.
I also know enough about plants and their growth to know what is required to grow plants to a certain level with a certain amount of lighting.
The substrate will only get you so far. It can be fun to play with, but the most dramatic improvements in growth are with the water column and that's something you can measure and get a rate. Substrates function as a nutrient pool if something in the water column runs low.
It's important and certainly not something you do not want to work on, but the water column plays a more dynamic role in terms of growth for aquatic plants. Some plants need iron in the substrate more than others.
Other plants seem to prefer aerobic substrates more than others.
He adds the liquid ferts regularly, and they have NPK in there.
If you dose daily, you can keep lower nutrient levels, but this does not gain you any advantage which Amano seems to believe for some reason.
But many believe "add just enough ferts" for the plants. this requires you to get a feel for the amounts and the ebb and flow of nutrient uptake and plant health in your tank. That's not something I or anyone can tell or explain to you over the web.
I've had 5-10x those amounts he states and great growth similar to what he has in the photos.
He seems to spend most of his time doing aquascapaes and photography, not measuring levels or trying new dosing routines or playing with light spectrums and CO2 levels.
He also gave no reason for turning CO2 off at night other than it's "Taboo in Japan".
A person can make even an odd method work, but that does not mean the method is good for most folks or repeatable with your tap water.
The other thing about the measurements: what type of test method was used and at what point in time was the measurement taken, like the time of day and also relative to the large weeekly water changes.
It's interesting his large water change routines and my own suggestion to that effect were arrived at independently. Dutch also did this. They had tap water with high NO3 and PO4. All they needed was K+ and trace and CO2. I had tap water with high PO4.
So who knows what the test mean. The routine is what matters, not some time slice of some measurements. That's not quite useless and certainly misleading.
River flows are often very low in nutrient level but they are not depeleted due to unidirectional flows, when applying this a tank which is more like a small pond, this level would quickly be removed.
Rivers have high algae growth like some lakes even at very very low levels of nuttrients, so the low levels of nutrients, in and of themselves do not help reduce algae.
The NO3 levels in my study site are around 0.5ppm NO3 and I used the best testing method available in the state of FL. Algae is highly abundant at the site, so is plant growth.
Hope this puts some of your hoopla over his measurements.
I'd not worry as much about that, look at the designs though.....they will help you
Regards,
Tom Barr