Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Only the general concept.
Yes, plants will remove nutrients from the substrate. That is how they survive. All over the world.
When the soil has a good cationic exchange capacity then the nutrients are held in a way that plants can get them. As some nutrients are added via water column dosing, they work their way into the substrate and take the place of the nutrients that the plants have removed.
So he is right in that plants deplete the substrate (especially a substrate without cationic exchange capacity) and can then be deficient in certain nutrients, and grow poorly or even die. The altering levels of nutrients and the plants' responses sure can be linked to increasing algae growth.
But that is not the end of the story. Set up the tank with good reserves of nutrients then replace the nutrients as the plants use them, before they reach the low level that induced deficiency in the plants. If you have slow growing plants then you might not need to be quite so diligent in staying right on top of replacing those nutrients that the plants are using up. If you have fast growing plants then you will need to be quick to replenish the nutrients those plants are using.
When I was switching fro very low light to better conditions for the plants, including adding carbon, I also started dosing with the EI method. I altered the recipe to accommodate the other sources of certain nutrients, but basically was supplying plenty of excess fertilizers then doing a big water change weekly. Most of the tanks have a high CEC substrate (Soil Master Select, Eco Complete). I ran the tanks this way for a couple of years.
When I slowed the dosing the plants continued growing well for several months. The high CEC substrate had accumulated a good level of reserve nutrients.
I think this is a good thing to consider in setting up a tank. Make sure there are good reserves of nutrients that will be released slowly into the substrate.
Continue to add nutrients to replenish the substrate before it is totally empty.