Which tank?

Here's one to ponder on...or for me to show my ignorance!!

I have a 29 litre cold water tank with some goldfish in (my Daughters) and a 30 litre Biorb with 5 Black tetras. The Biorb is nice and warm the cold water is BRRRRR!

Both tanks are mature with filtration etc.

Thanks to an offer of some L100 youngsters I am wondering about swapping the Tetras into the coldwater tank (after adding a heater and some heat!!) and putting the goldfish in the Biorb as I think it will be easier to manage the small BN in a conventional tank.

The young BN's will then go in with the tetras (or the tetras can go into my trigon) BUT will the 'good bacteria' survive a fairly sudden temperature change or would I be asking for trouble? Will the tetras be a good mix with the young BNs (approx 1 inch long).

Thanks

Sounds ok to me. I would do the temp increase and them shift the fish around. Goldies can live in warm water so do the increase, make sure all is in order then do the shift around.