Someone please explain why you don't have to Cycle each time you change the filter.
Because you don't (or shouldn't) change out the biological media in your filter, which is where the bacteria lives. You only have to change the chemical media (carbon, if you even use it) and the mechanical media (only when water flow slows to a trickle and rinsing the mechanical media in tank water does not increase flow).
. But you do eventually have to change out the filter when the flow of the water doesn't go through it. So?
What sort of filter is it? It sounds like you have a HOB filter. Which kind is it?
& to piggy back on this - The media does house majority of the good bacteria. Keep in mind that the good bacteria is not naturally free flowing (as in you can find free flowing good bacteria but in order for it to thrive it needs a host) & also attaches to gravel, decor, & the aforementioned biological media. Long story short, it's the reason "seeding" speeds up the process. It helps spread the good bacteria as it's already colonized. It now just needs to expand. Filtration changes as long as the gravel & other decor is not removed as well won't trigger cycles as the good bacteria is already formed in other areas of the tank =) I suggest rinsing off the slime. That's really the extent of things. Don't just toss it... It holds the key to a healthy tank in all that fish poop! =P
I have a super Clean 50 HOB with a lot of extra media, porcelain rings and stars. But my small tank only has the filter. I did put some stars in there. But if it didn't have the extra stars. when the filter fell apart you would have to replace it. There is enough bacteria in the gravel and plants and decorations?
If you need to replace a filter, simply save the media (rings, carbon, etc). If you need to change the media, maintain the filter. Replacing EVERYTHING would cause what some claim to be a "mini cycle". When I replaced a canister filter on my 125 gallon, the new filter caused a mini cycle. I utilized all the same media with the exception of the newly shaped sponges that comes with the fluval FX6. The cycle lasted 2 days max & had no effect on the fish. I certainly don't want any fish to be in a tank when it cycles but I didn't expect it to happen then either. Depending on the size of the tank, a mini-cycle may happen when swapping out all the media. A common mistake that people make is simply tossing their filters once every few weeks. All it needs is a rinse. Each time they toss it, they toss the main colony.