Yep thinking about it I’ve dumped all my sponges now, use to have em in my old Eheim pumps but now run em without. The reason I suggested cleaning in this method is that the sponges become Nitrate factory’s and rinsing them in tank water doesn’t address this problem, you could boil RO water and use that but the tiny amount of water left in em after you’ve given em a good squeeze I wouldn’t bother. As I said I don’t use sponges anymore but I do use a bit of floss in the sump as a mechanical filter and this I treat in a similar way :)