Your right, I didnt mean to imply that it needs medium light but that it can do fine in it as long as algea is not allowed to build up on it, same with the gorgs as well. thats another reason why all need good current and sponges need to be dusted off periodicly anyway.
Not much reason to have one if its not lit up to see it I think. Ball sponges are generally pretty hardy placed lower in reef tanks if the owner take care of them properly. Thats sort of why I mentioned the established tank part. Sorry I wasnt clear on that.