Your turtle isn't nearly as sensitive to an uncycled tank as fish are. Remeber your turtle can crawl out of the water when it wants to. I definitely understand the desire for the cycle to complete when you are waiting to add fish.
You definitely want carbon in a filter in a new tank to pull the chloramine out of the water. Once your tank has been cycling through the carbon for a day or so, you can replace the carbon with Purigen OR run them both at the same time.
Carbon and Purigen can co-exist together. Carbon and Purigen have much overlap as to what they will pull out of the water. Carbon is great in a new tank for pulling out chloramine. Carbon however does exhaust itself in a few days to a few weeks depending on how much crud is in your water. Once carbon has been exhausted it doesn't absorb any more.
Purigen is synthetic resin beads that has a huge affinity for nitrogen based organics. You can clean and reuse Purigen quite a few times before it needs to be replaced. Purigen claims to grab 2x the amount of gunk out of the water when compared to carbon. I belive this claim is a bit low. I've talked a few others on this forum into trying Purigen and they have reported back saying they noticed a drastic difference.
Here's what I would reccomend for anyone with a new tank:
First 24 hours:
Run your filter with some carbon and as much filter floss as you can reasonably stuff in there. The filter floss will grab any free floating particles from the sand (assuming you used sand) and polish the water. The carbon will grab the chloramine out of the water. Any chlorine will just evaporate.
After 24 hours:
Ditch the filter floss and the carbon. Put your sponges back in. Put in a bag of purigen. Fill the rest of the filter with bio media. Happy turtling.
Your bacteria colony will establish itself on all surfaces in the system. The point of the bio media is just to provide as much surface area as possible for the bacteria to colonize.
Getting used water isn't really beneficial. It's just, used water. There's a very small amount of free floating bacteria and stuff... but the bulk of the bacteria is in the filter media and sand.
