<<< Was meaning to ask you what kind of growing regimen do you have for parodia's and rebutias, ( I saw a bunch of plants in one of your pictures)! Are they particularly difficult, require any special treatment? Thanks
Oh my goodness, these are not easy questions - if you take it seriously. . .
Parodia are very different.
](./images/smilies/eusa_wall.gif "Brick wall")
Parodia / Eriocactus are straightforward, a lot of water - much fertilizer - much or less sun.
Rebutia are not as complicated they grow like crazy.
A lot of water - much fertilizer - a lot of sun - many flowers!
If I want to know how I have to maintain a plant, I look where it grows.
I do not look in Cacti forums.
I look at maps, rainfall charts, temperature charts.
Then I think about it a little.
If plants grow in the mountains, they rarely get 100% sun.
I look very much to Habitat pictures.
As you can see then, many cacti growing in the grass, under trees and shrubs.
I draw my conclusions. Very few cacti live in 100% sun, in the desert without any water (0%!!!).
For us plant lovers it is difficult to implement advice 1 to 1.
The housing conditions, the climate, the greenhouse, the substrate, the light, the temperature, the humidity, the watering characteristics - everything is different.
And all this plays a major role! Resumé: not a panacea!
Trial and error (not the best way, but simple.)! Observing, patiently try to think without bias.
I'm learning every season, every day. And I'm miles away from a satisfying result. 
Best wishes
K.W.
We are all in the gutter, but some of us are looking at the stars.
