Outlaw, Let me see if I can recap this.
You are buying a used tank with a
new filter and gravel,? which you will be picking up next Sat. It has fish and all are going to be transported with only 5 gal of water. Your problem is you don't think it is cycled? Is this tank cycled, or not? Is the filter and gravel in this one new or old? If it is all cycled and you just need to transport it, put new water in and go, you CAN use water out of the house tap at approx the right temp, and it should be good to go, as long as you have the dechlorinator in.
Just make sure to use a thermometer as you fill. If you have kept the filter and gravel all moist and approx. the right temp while you transport, the bacteria should be fine. If you are transporting in a 5 gallon bucket, it should be ok to keep the fish in that for several hours to overnight, if you slip a heater in, and air stone.
Or are you only worried that your 20 g tank you are cycling now isn't ready for any fish, and you want to put the 6 new fish in there for the time it takes to warm water in the new (used) tank?
If that is the case, your 20 gallon could get a 50% change before you go pick up the new fish, and unless you are using 100%
ammonia to cycle it, your fish should be ok in this tank, say overnight till you have the used tank set back up just the way you want it. I personally think this would be much more stress on the fish than leaving them in the water they are used to in that 5 gallon bucket, till their tank is ready.
Either way, I think you can rest. How far do you have to go for the tank? Let us know how it all plays out.
