Switching filters in fish tank?

[kimkat]

I have 2 tanks running right now, one holds an almost cycled 3 gallon (nitrite spike) and the other a fully cycled 5 gallon. They both use the same AZOO mignon filter. Water parameters (as far as PH goes) is the same. Only difference is a slight change in temperature.

If I physically moved the entire cycled filter from the 5 gallon and move it to my 3 gallon, would my 3 gallon be instantly cycled and my 5 gallon almost cycled? Or would it only help kickstart the cycling process again for my 3 gallon?

 

[IllusionX]

You would probably hitting a mini cycle in your 5g, since you are removing more than needed BB from it.
I would just leave it like this since the 3g is almost there.

What you should have done in the first place is put both filters in the 5g to seed it. Or at least stuff both media into one so you can split it later.