Required reading: wetland soils text, please read if you like to learn!

If you like to learn, and can read past some of the stuff you might not understand, then this might explain great deal to you:

Wetland Soils: Genesis, Hydrology ... - Google Book Search

You can look at the figures in particular. Wetland Soil is a very dynamic thing and it can explain a lot about how and why it works in aquariums.

ADA soil, potting soil, how you can prep things to avoid issues, how things cycle in the water column to below to the root zones, how the root zone affects nutrients and bacteria and O2, why heating cables are a bunch of baloney, you learn this stuff, you will have the power to see and understand these issues for yourself.

Do not take my word for it, read and test and see. See is my old professor Dr Reddy is up to par in what he taught me in Wetland soils at UF.
See if this text sounds reasonable in light of what I have been saying for years.

Yes, it's sometimes complicated stuff, but do not let that deter you from learning and gaining a few pearls of wisdom.

Learning can work and it can be interesting.
It can and likely should challenge you, much like a mystery novel/book.

Regards,
Tom Barr