Upgrading & cycling?

[laurelhed]

I want to upgrade my 20 gal freshwater tank to a 40, but here's my question-do I have to completely cycle the new tank like a new tank, or can I move my fish over with the plants, used filter media, and most of the water from the old tank? Of course I would wait a week or so and check levels before moving the fish over.

 

[Nimo]

If you use your old filter media, some of the substrate, plants ,deco and water from your established tank then no it is not like doing a completely new cycle.
That is how I have started several tanks. With some of the new ones not even so much as doing a mini cycle.
You can move your stock as soon as the water clears up but let the new tank run for a couple weeks before adding any new stock and you should be perfectly fine