Hello; I like to keep a QT ready to recieve fish at all times. To me this means that the QT needs to have been cycled and a population of beneficial bacteria (bb) alive and in place.
I do this lately by keeping a small population of fish in the QT along with some ramshorn snails and a sometimes a bunch of live free floating plants, usually hornwort. Currently I have several white cloud mt. minnows in the QT. I bought them six to eight weeks or so ago and at some point they will go into a tank with other white clouds and a large school of neons. In the meantime they are doing well in the QT and along with the snails are keeping the bb going.
When I run across some new fish to buy the white clouds will go into another tank and the QT will be ready to accept the new fish for a few weeks. This also keeps the QT ready as a medication tank in the event I need to isolate a fish for some reason.
A QT can be up and running quickly from empty if something like a sponge filter or established filter media from another tank is kept available to seed it with bb. I found some open cell foam (sponge) material a few years ago at Wal-mart that I used to replace the decades old material of some old sponge filters. It is thin enough that I can have two layers on a sponge filter base. This way I have a bb loaded source that is easy to add to any new tank for a quick setup. To get the empty QT up fast i siphon some water from an established tank which is already up to temp
during cool weather and the water is conditioned. Then throw in a sponge filter with a half new sponge and a half sponge already loaded with bb. Add a heater if needed and some floating live plants. The tank is ready in short order.
I have done QT's both ways and made each work. There are likely other ways to deal with the issues of QT's.
