i regularly set up a "new tank" when i need to house fry, it's 300L and this is how i do it.
1) I take substrate from the existing tank and put it in the new tank. Enough to cover most of the bottom.
2) I then use water taken out of the existing tank to part fill the new tank, maybe 1/3 of the new tank.
3) add the heater, air and new canister filter.
4) fill new tank to level desired and add fish as long as temp is somewhere near what it should be. Maybe fill it over a few days.
5) do a 25% water change 3 days later just to be cautious.
This works for me very well and has not posed an issue in the dozen or more times i have done it this way without using an existing filter, with an existing filter you'll be fine. I think the key is the substrate, it must hold some or a good amount of the bacteria required. I generally am only adding 6 to 12 fry to 300L so the bio load is very little as well.
If i was to use an existing filter i would still change the substrate and some water, doing that is just basically changing tanks and doing a water change.