Anything organic will produce the food for the BB to maintain the nitrogen cycle without a fish/Betta in the tank....like live plants, shrimp, snails....etc....anything alive will produce the byproduct needed.....
Repost: If my betta fish DOES pass away at some point in his life (I hope not soon or there will always be tears regardless) what would I do?
His 5 gallon is fully cycled, but how can I keep dosing ammonia to keep the cycle continuing (before I add a new betta, of course) if there are 2 Amano shrimp in the tank?! They will surely die! & we all don't want that.
The carbon itself is short lived/used up and can't be recharged-and the carbon needs to be changed per package direction if you want to use carbon. Using carbon is a personal choice and not needed IMO/E, however, having some fresh unused carbon on hand for emergency is a good idea-it has saved me more than once-but I don't keep it in my filters all the time.
The sponge part is good to use until its falling apart-but it needs a rinse/swish a couple of times a month or the BB will suffocate with the buildup of mulm/debris that it collects.
With the filter cartridge that are both carbon and sponge-you can either cut a slit and dump the carbon or leave it-Once the carbon is used up-its used up-but it won't hurt to leave it and will even provide more surface area for BB to colonize.
A lot of the BB are in the substrate, on the walls and on the decorations too, when you are dealing with really low bioloads- you usually can change out your filter media without issue, however, its always a good idea to monitor for spikes and make that extra water only changes if needed.
Also, you don't need to use charcoal and change your filter out all the time-its a personal choice-it won't hurt to leave the used up charcoal in the filter or you can cut a slit and dump it out saving the sponge part and giving it a rinse/swish a couple of times a month.
My 5 gallon tank is cycled w/ carbon filters... since they must be replaced every 4-6 weeks, what should I do? All the BB is in the filter!
Should I cut the filter open & pour out the carbon, then shove that UNDER the new carbon cartridge? I have 3 extras of these & they go w/ my tank. Please help me!