Eggs???

I don't want to come off as ignorant but I've just gone to change my one (of 2) filter in my tank (3 female ADF... I think?) and I have never seen anything like this in the filter before, I also have four Zebra Daino as well as a ghost shrimp,. Is this just some kind of funky algae or is someone laying some eggs? All my parameters are good and rinse this filter every 2 to 3 weeks.