A min-max thermometer is essential to keep track on the temperature changes. I would not recommend the use of Paraffin heaters as they are difficult to control produce water as a by-product of the combustion. The colourful flower of Pelecyphora aselliformis . A crest or 'cristate' shape emerges when the vegetative point grows very evenly but repeatedly divides into two. The crest curls while already growing in all sorts of curved shapes.
Monster shapes almost always have to be grafted to stay alive.
There are some specialists that only collect cristate cacti. There are many variations of cristate that occur in all shapes sizes and colour. As a general rule very few produce flowers, but are still attractive because of their unusual appearance. A freak form of the species Gymnocalycium mihanovichii is 'Gymnocalycium mihanovichii cv hibotan'. The unusual colouring is due to a lack of chlorophyll when the seed was germinated .