Having, and not changing the filter cartridge would be ideal as the main benificial filter bacteria is store in the cartridge. Changing it would surely end in disaster as the ammonia, would spike leading to dangerous levels of it causing stress and sickness
I replace my filter every 2-3 weeks but i got 2 aqua-tech 10-20 in a 20 gallon long tank, so what i do is i replace them one week apart, but isn't the carbon inside the filter suppossed help you get rid of ammonia and that is why you replace them or is that just a scam?
Carbon clears the water, cleans excess nutrients, Eliminates tannins, etc. the one hat eliminates ammonia is considered zeolite. But your main concern when changing any type of filter media is that it greatly effects the filter bacterias colony, and numbers. With fewer bacteria. Your tanks ability to eliminate toxic substances such as nitrites, and ammonia diminishes greatly, meaning that they will spike resulting in mass deaths, and most likely. Many sicknesses to break out within the tank
Depends. Do you want your carbon do be doing the things Mo said? Personally, I don't, as I use fertilisers in my tank. If you want the activated carbon to continue doing that kind of filtration, do continue to replace it, but for other media, yes, just rinse.