In reading your other post Joelle (Set up my QT!!!!
), it sounds like this is the tank that you are treating your 2 fish in for ich, using Coppersafe? If so, a few things...
The reason you're seeing ammonia and nitrites is because the tank was never cycled. Putting water from the display tank in the quarantine tank does not cycle it. The bacteria that convert the ammonia are not in the water. A quarantine tank needs to be cycled just like a display tank.
HOWEVER... since you're using Coppersafe in the tank, most likely the bacteria would end up dieing off anyway. Frequent water changes will be necessary to keep the ammonia levels down to a reasonable level, if not zero. Not sure what your levels are (3rd color down?) but just guessing from your nitrite levels, your ammonia levels are probably a tad high.
When doing water changes, you'll need to make sure the copper concentration stays at the level that is required for the stuff to work. This will most likely be noted on the instructions somewhere, and also means you should equip yourself with a copper test kit.
Like others have mentioned, not sure why you diluted your 8g of tank water with 2g of fresh RO
water, but yeah... I imagine your salinity took a drop pretty quick there. In addition, if you're treating for ich, it's probably not best to use the display tank water in your quarantine tank. You're just bringing in more ich. Use new saltwater for the QT.