quick question!!

[Marx]

can you cycle a small tank with 100% water from established tank?

Im thinking to setup a 20gal puffer tank.. with water from my 75gal..

can this be done?

[gvv]

I did it. With water, plants and filter. The next day I put first fishes there without any problem. I should mention that I didn't put all fishes from old tank to the new one, just in portions during the week to balance the load.
Fishes were small: SAE (plus shrimps), Ottos, Bettas, kribs. In this order. After a week or two I had the kribs fry...

[BigDaddy]

Marx...

While there may be some bacteria in the water, they prefer to colonize on oxygen rich surfaces.

So, filter media first... then decorations and gravel, and last in the water itself.