Couple things based on what I read, from various scientific articles and a little personal experience.
The only sponge that's filtering water is a healthy sponge (a dying or dead sponge will pollute water)...
Sponges consume from sub micron to maybe 10 micron (species dependent)
Nanno. algae are about 2 microns, some sponges can eat it.
Some sponges are calcified, some are not.
Sponges don't like high phosphate (I read this in a study)
Sponges don't like salinity swings or low salinity (experience + read this)
Sponges need some silica to grow/repair/regenerate
Some sponges will " shut down " for a few weeks to consume the food they caught, and then reopen after
Just some random thoughts...