Hello and welcome !
Stability is used to help jump start your bio filter for those who don't want to wait the 5-8 weeks needed for that. ( cycling )
Pristine is for helping to break down the waste in a tank. A proper bio filter will take care of that.
First a turtle can go right in a new tank it does not have to be cycled , they breath like us ! If you have a good filter with a good media setup for a turtle having it in tank will help kick start the bio filter / cycling.
Good read :
viewtopic.php?f=9&t=30145Now if you want fish in there to ( good fish) then cycling the tank is a must for the fish. But they will only become turtle food !
Most long time turtle keepers are trying to keep thing's / chemicals out our water ! I have Not used any chemicals for decades. I am old school and let nature help me , it seems to do well on its own. Once you start with chemicals , one for up and one for down.... most tend to stay with chemicals. That's not for me , it's your call on that.