I just started my first walstad tank (see picture with the cat lying in anticipation: )
It's pearling like crazy as there are no fish in and I just filled it yesterday.
The substrate is low-fertilized topsoil for cacti, about 1 inch and about an inch
fine white sand.
The plants in the pots (back left) are waiting to be planted (or not?) because I'm not entirely sure
how many plants I need for the tank to be (almost)self sustaining.
I'm curious to hear your ideas about it!