Bacteria growth in established tanks

[connor31556]

Hi guys I have a perfectly fine 20 gallon tank with alot of media in the back which has been cycled for a couple years now. However I have recently added a filter cartridge from another tank witch is not cycled at all (new cartridge). My question is how long does it take the bacteria to spread and grow on the new cartridge in the established tank?

[fishwonder]

If you just plop and drop the media in, 2-3 weeks. Best to squeeze that media into the water itself so the brown gunk good bacteria will now get sucked up by the new filter media and start your cycle in 4-12 days. Might be better is to replace everything in your new filter with as many simple pot scrubbies that will have better flow through the media and not get clogged. Won't have to rinse out those for like 6+ months.

[Delapool]

Would also say two to three weeks from some testing they did on replacing filter carbon (but have not tested myself).