Hi Everyone! How long can I leave a carbon out of the tank. In my 20 gal tank I have 3 black moores, and 1 baby pleco, It has been established for over 2 years, 5 days ago I took the carbon out cause I noticed one of the black moores had a bit of fungus on his dorsal fin, didnt seem sick or anything but I took the carbon out and treated with primafix. Today I did a major tank clean...took all the ornaments out and gave the gravel a good vacuming, cleaned filter and powerhead. I just rinsed the sponge for the filter out and reused it as its only a couple of weeks old, and I rinse it in my aquarium water that I took out...I went to put a new carbon in and Im out!! Big Snow storm here so I cant get one till tomorrow. Just so I know....What is the purpose of the carbon? I know it keeps the water crystal clear...but what else is it for? Thanks for helping!