OK, might have missed something, so if I did then sorry (read through twice), but OP said he set the tank up on Monday, it's only Wednesday now, no way is he gonna have any bio-filter in two days (unless media was taken from a fully cycled tank). I'm pretty sure the 'testers' that hang inside the tank take a good 24 hours to 'settle' before a reading can be taken and even then they are not accurate at all.
Sounds to me like the tank is just begining to cycle, in which case Ammonia is going to go up to dangerous levels very quickly so something like Prime is needed to protect the fish right now. Add Stability as well every day (follow instructions on bottle) to try and move the cycle along quickly or there could be some dead fish.
Like I said, if I misse something then sorry, but better safe than sorry!