Cleistocactus strausii
As a houseplant, the Silver Torch cactus is an easy to take care of so long as over-watering is avoided. To naturally simulate the porous effects of the sand in its native habitat, it's important to ensure that excess water will not pool in the soil, causing the roots to become water logged.
This plant’s native habitat does not have winter, but when temperatures drop to the low twenties, it can exhibit signs of tip frost. 
The Silver Torch cactus is most susceptible to 
mealybugs 
and spider mite.
Orbea variegata
This plant is popular in cultivation, and is often sold under its former name "Stapelia variegata". It has many common names, including starfish plant, starfish cactus, carrion cactus, carrion flower, toad cactus, toad plant. It is not closely related to the true cactus family.
When grown as an ornamental plant in temperate zones it requires protection, as it does not tolerate freezing temperatures. It is best grown under glass, in similar conditions to cacti.