I have a small 2.5 gallon mini bow. I am planning on putting together a 5 gallon planted tank. What is the best way to transfer the good bacteria from my 2.5 gallon tank to my new tank? Would a piece of filter material suffice?
If it is planted enough and the inital bioload (amount of fish) isnt too high,then it wont need cycling.You can you use filter media to be safe (or if its not too powerful,you can run the filter for the 5g in the 2.5 for a while alongside the original filter).Also you could place ornaments for the 5G in the 2.5 for a week or so to gain some bacteria on their surfaces.
Or, if you're not keeping the 2.5g up and running, you could just move that filter (and the decor while you're at it) to the new 5g. After the tank has been running for a while, you could probably remove the 2.5g's filter from the 5g tank, leaving just the filter meant for the 5g, and not face a mini cycle. If you plan on keeping the 2.5 running, though, Tomsk's advice is the better route.