Just growing or rotten?

[Ned_Fellenor]

Hi everyone I have recently started collecting cacti and succulents. I have some older ones given to me and some new ones I bought myself.
They are doing well for the best part but this one in the picture I've attached of a cactus has been drastically changing. When I got it just over a month ago it was completely upright and fine.
I put it next to my large windowsill so it has a great amount of light. However it has changed its shape and direction so quickly I'm alarmed by it. It has been moving towards the light but I am also worried that it could IN FACT be the case that its rotting? I have watered it once since I got it which was about a month ago and I do not know how long before that the owner watered it (Maybe they watered just before they gave it to me, maybe they did it 4 weeks before etc). I am a novice which may be overreacting but I would like some more expert advice to tell me if its just changed direction very fast or if its rotting.
Thanks.

[Brunãozinho]

It needs more light, and it's not the only one that needs more of it. Maybe you can find a better place.

[DaveW]

Chamaecereus silvestrii as it used to be known, or Echinopsis chamaecereus as they have now dubbed it, is a naturally sprawling plant, yours is however leaning towards the light as Bruno says. Terrestrial cacti are high light intensity plants and will tend to lean towards the light if it is mainly coming from one direction, as within a room rather than outside or in a greenhouse. More light also keeps the stems shorter and more compact:-

http://www.botanic-gardens-ljubljana.co ... silvestrii" onclick="window.open(this.href);return false;

[Ned_Fellenor]

Thank you very much I'll consider moving them in that case.