On both my 38g and 20g aquariums I've got HOB filters, which are doing a good enough job of keeping things clean. However, lately I've been considering putting a canister on my 38. While the Aquaclear HOB on it seems to be performing well enough, it makes a bit of noise. I've checked and cleaned the impeller and all seems to be working properly. The filter's cover amplifies the sound making it a little noticeable.
While I can live with it, I've had thoughts about swapping to a canister, probably something like an Eheim 2234. The questions that spring to mind, though, is how long I would need to run the filters in tandem and how would I know when the new filter is 'ready.' Obviously I'd need to leave the HOB on until a canister was able to get a good population of bacteria going. Since it's cycled tank, I figure I could use some media from the HOB to help get the canister started. Is there any way to tell when the canister was actually able to support the cycle without just shutting down the HOB and testing the water daily?