Cycling a tank and filter media question

I have a 5 gallon Topfin Integrated Filtration System aquarium for my daughter



The filter cartridges are the mesh type filled with carbon. My question is about when I change the cartridge...I've read that carbon isn't necessary. So when I do change the cartridge, what do I use? Can I just get some of the foam/sponge filter media and cut it to fit? Or do I get the Topfin replacement cartridges meant for this particular filter?

Also, I've got a betta and the tank is on day 17 of cycling. Ammonia is staying at 0.25 and nitrite is 0. I'm doing 25% water changes every other day. My question is concerning the nitrite...thought it'd be present by now. (In my other daughter's tank it was present by day 10.) Do I need to do something different, or just give it more time?

 

Do not change your filter till its really Really REALLY bad. Your still cycling don't take away the BB.

Did you use a bacteria product?

 

Only product I add is BettaSafe.
Do I need to take the carbon out of the filter when it's a month old...I read where it starts leaking toxins after a while?

 

Like muss... said, you do not need to change your filter cartridge, but if you'd like, you could certainly cut out the carbon and either toss it, or leave it in a mesh baggy in the tank. Personally, I've never had a problem with my carbon, and it's been in there for a while. If your cartridges get extremely dirty, you could rinse them in dechlorinated water and put them back into the tank.

These are my cartridges.

I cut the carbon out and put it in a separate compartment. Also, just so you know, your bacteria isn't always in the cartridge, and it's most likely in any part of your filter that is supposed to hold the bacteria, so don't be scared to replace them if something bad happens. My filter consist of a bio-holster (meant to hold bacteria).


Replacing your cartridge with an aquarium sponge works, too, and it's what I've done to my 2.5 gallon minI tank.

(obviously you might want to make it fit better, mine is temporary)

 

Don't worry about filter pads with carbon. Wait until you have 0 0 10-20. I would use prime. It detoxify harmful ammonia and nitrites during cycling.

Since your stock is low I would let the filter go almost 2 months. I could be wrong but the higher the bio load the more filter changes needed.