Ive done thisthe hard way....
Get a new filter and run that in the current tank.
Get some containers and the new heaters for new tank if your house is going to be cold or you are diong this alone (i do not recommend doing it alone!)...
Then.... on the big day.... this is what i did...
New tank sat on floor, clean and empty.
Transfer from old to new tank about 3/4 of the water (or more depends on size of old tank and how mucky it gets when you get down low and have loads of silt and plants to rip up)....
Transfer fish to new tank currently on floor, run heater and filter to keep it at right temp.
Empty out entirely, old tank, inc of substrate etc, give it a good wipe out. Put this on floor.
Start to shift water and then fish from new tank back to old tank, ditto filter n heater if poss.
New tank now empty, move into position vacated by old tank.
Put in new substrate (wash it!), plants etc, and slowly fill with warm new water.
Carry on filling with old water from old tank, put in heaters and A filter from old tank (remember you have two now), leave fish enough water in old tank .....
Put in fish or, if new tank very murky leave it an hour or so to settle and then upt them in.
Transfer last of water and other filter.
This ensures you have basically a cycled tank, when you are sure its ok you can remove the old filter if you wish to use it on teh old tank elsewhere. Running two filters on a newly set up tank isnt a bad plan especially if you have to shift the fish over straight away as it clears up any murkiness.
Ive done this TWICE now and whilst its a pain in teh rear of a job it gets it done in one day.
If you do have suitable containers and safe quieti places to put them to put the old tank water and fish into whilst you do the swap, do that instead, as its going to be less stressful - i didnt have either containers or a safe place (too many nosey dogs not enough safe rooms to shut them in) so did it this way.
Em
