I'm wondering If you can Open these to replace the carbon Inside them. I'm currently Still running At least 1 Under gravel filter In my 10 gallon,because I bought a sponge filter for the other air tube to go in.
So again I'm just wondering If I can Actually open these things Up and replace their carbon I mean I've been trying to but It Doesn't even budge. My friend bought me some carbon for it,But I cant even Open the Cartridge.If I'm not mistaken Its a Penn-plax cartridge.
Sorry for the fuzzy picture I just Uploaded what ever looked like the ones I was using