Setting Up My New(used) Aquarium

HI guys!! I'm about to start setting up my new 30 gallon cube. I pretty much have nothing for it yet.
Questions:

1. How long can it run fishless with used media before I start to kill my bacteria?(needing to know so I can sync my QT and cycling time)
2. I planned on getting some platies today and maybe even some rasboras or CPDs(those will be for my 20 gallon tall once I move all my aeneus to the 30 gallon). Since this is a new tank with nothing in it and will be pretty much cycled already with used media and/or rock/decor could I skip the QT time and just put my platies in?(I would of course wait some weeks before I got anything else and then properly QT those from the healthy platies).

Thank you in advance!!

 

1. 4 days, I’m pretty sure, but there’s a lot of different info out there.

2. If there’s nothing existing in the 30 gallon then you don’t need to QT, just QT any fish after that.

 

1. 4 days, I’m pretty sure, but there’s a lot of different info out there.

2. If there’s nothing existing in the 30 gallon then you don’t need to QT, just QT any fish after that.

2. YAAAY!! My kids will be excited lol.

 

2. YAAAY!! My kids will be excited lol.

If you really want to do a fish-in cycle, I’d pick up some SafeStart Plus and Seachem Prime

 

If you really want to do a fish-in cycle, I’d pick up some SafeStart Plus and Seachem Prime

Already got it all. Lol.
I used Prime on my 10 gallon. I dropped in a used sponge and large lava rock from my 20 gallon. Let it run for about a day then put in 3 mystery snails and used Prime for about 3 days. I saw a small spike in nitrites about day 2 never any amm and by day 4 nitrites and amm were 0 and stayed that way.