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.
Parodia leninghausii
As most of the cactus, they need well drained soil, sunny exposure, regularly watering in summer and not at all in winter. In temperate climate, keep them outside in summer. In the wild and in winter, plant accepts frost at -4 °C if totally dry. In cultivation, it is preferable to keep cold temperature, but more than +2 °C.