I see pineapple sponges, harmless filter feeders found in darker higher flow areas of tanks, sumps and over flow. Population typically decline as the tank ages.
Probably but not something commonly found in the hobby.
Most consider them a natural part of the bio-diversity of a system. Having you been add silicates to the system? Populations wax and wane based on available nutrients within the water column.
I use frozen foods and phytho and zooplacton to feed mi corals so is natural that they spread a lot... I was thinking in some predator that put them in control because they are invading mi skimmer sump refugium also...