Upgrade

[Mudge]

If I upgrade from a fully cycled 10-gallon to a 20 or 29 gallon by using all the same substrate/plants/filter media, can I expect (or at least hope) that the new tank is likewise cycled — or close to it, anyway?

 

[connorlindeman]

Closer then a fresh start, yes. I wouldn't fully stock it for a bit though. Monitor parameters.

 

[Innesfan]

That's how I do it and it's worked every time. I haven't started from scratch with a cycle in several decades. As @connorlindeman suggested, monitor parameters and ease into stocking.

 

[Colin_T]

Yes, the tank will be fully cycled because you are using an established biological filter.