2 weeks for bio filter?

[goldfish freak]

Hello, I would please like some opinions on if 2 weeks is long enough to establish a substantial amount of nitrifying bacteria in a bio filter that has been added to a established tank? I added an additional filter to my 120 gallon with a single fancy goldfish. Could I sucessfully cycle a 20 gallon tank with a single goldfish of approximately the same size using this bio filter? Would I expect to see a ammonia or nitrite spike in this 20 gallon, or do you think the filter would be mature enough to handle the bioload?

[brianfl]

It's possible but 2 weeks is really on the low end. It also depends somewhat on the type of filter. Is it a bio wheel type filter? I would give it another week or two myself.

[wetmanNY]

Why not cycle with the mature filter?