She did say a gentle bubble to promote water movement, but yeah I was thinking the same thing you were re: co2. Glad you liked the article. I'm wanting to pick up a few 2.5g with glass lids now, with some organic potting soil.
No I'm going to put a small fake plant in it, idk if I should use some of the sand I have or if should but some glass marbles at the bottom. It's going to be a Birthday gift for my mother in law. She already has a Betta I'm just going to give it a nicer home. I offered her a 5gal tank before but she said it was to big for her to move around so this is a nice option.
I believe the organic potting soil adds a source of nutrients for plants as well as the micro organisms for a balanced system. Not sure if you'd have to let the tank cycle with the micro organisms, or if it's safe to immediately lightly stock... Im curious/leery about the "no water changes" part. Been trying to look for more reading, may get Walstad's book.
Tom Barr (Plantbrain) has a similar low-tech non co2 technique which I believe just uses sand & mulm.
I'd think you could use smal-sized gravel or large-grain sand & include root tabs (or ADA Aquasoil) for a similar affect.
I was thinking of using that as a cap fir the soil myself...
From what I understand, Eco-complete draws nutrients from the water column & makes it accessible to plant roots - it doesn't have nutrients on it's own (I think I got this from Dundadundun but I may be quoting wrong).
Nonetheless I don't see why that wouldn't work with occasional tiny doses if flourish or dry ferts to the water.