Swapping out tanks with new fish
I posted this in the getting started section but figured I may have better luck here.
I am completely new to this forum, as well as this hobby. A couple weeks ago I purchased a 60g tank/stand kit from PetSmart, and set it up about a week ago with 2 platies and 2 mollies to get the nitrogen cycle going. Almost immediately after putting them in, I noticed a small scratch/crack in the tank. I didn't think much of it but took it to a local aquarium store and they advised I lower the water and replace the tank ASAP.
Petsmart has agreed to replace the tank. However... they will not get another in stock until Saturday. This past Monday, I lowered the water to about half so it wouldn't cave, but the filter won't work with water that low. Fortunately, my neighbor happened to have a tank of equal temperature and fish compatibility, so they are staying there for now.
So my question.. When I replace the tank on Saturday or Sunday, is it better to fill it up with the water that is still in the old tank, even though it has been sitting there idly without a filter running for a week? Or should I just fill it up with dechlorinated tap water and start the cycle over? Any other advice on the situation would help as well.
Thanks in advance for the replies!