They do look like pineapple sponges to me as well. If that is the case, itís not an infestation of any kind, theyíre actually a very helpful filter feeder in your system. Itís a sign of healthy tank. I wouldnít do anything to remove them or change any course of action. Just let them be, chances are they will start to drop off at some point in time when your tank matures and outcompetes them for nutrients.
Fish tanks are just complex math equations, but Iím not good with numbers.