I bought the $31 FB off of eBay. I can't take the top off! The sand material inside is preloaded and the top is glued... So I have about a 1/4" hole to try to get the sand out and the carbon or ferric hydroxide in. Look on the bright side... it won't leak!
Man, that sucks. I would have thought that they would have screw on lids or a port to change out the media. Can you drill a 3/8-1/2 inch hole in the top and tap it so that you can screw in a threaded plug?