Hi MrsM3197!
well usually when bio-spira is added you are supposed to put in all the fish at once so that the beneficial bacteria doesn't starve cuz there is not enough
ammonia but by now I think you should just wait and make sure your cycle is completed.
add only 2 or 3 fish at a time so that your tank doesn't go through a mini cycle and that would work just fine.
Once you are sure then you can ad a school of 6 cherry barbs if you really like those and like 3 otos and that should be good for your tank. it's kind of overstocking so you should keep an eye on them if that's what you want to do.
you can start with 3 cherry barbs, wait a week and if everything looks fine (ammonia, nitrites & nitrates) then add another 3 cherry barbs, then wait again and add the 3 otos. that should work fine.
good luck!