Not sure how many have overflow boxes but on the sides there are large holes where the PVC
pipes come out which would normally fill that hole. On the particular overflow box that I found him in I did not have that hole sealed up with floss like I did on the other side but someone had sent me a picture of some plastic stuff that you can get at Michaels or Hobby Lobby – craft stores.. It is for either cross stitch or latch hook project. So I rigged this up and in hopes if I should get another one like him that he won’t end up like the last one. Sorry about the reflection in the one picture without the screen top on.