Join Date: Oct 2010
Location: Victoria, Australia
I wouldn't bother with bacterial supplements. It looks like your tank is cycled if your results are correct, but I would do a couple of tests over the next few days to see if it wasn't your large water change the other day that has brought your parameters down.
Don't do any water changes for the time being, and if your ammonia or nitrites start to rise, then you know your tank is not cycled.
Neon tetra disease can hit neons, but it has pretty specific symptoms and I don't think it happens overnight.
Media is the sponge/cartridges/ceramic noodles inside of the filter. This is where all your beneficial bacteria lives.
Just floating the bag may not have been enough if the fish were from a tank that had very different parameters from yours. 7.2 is not too high a pH, but generally you should acclimatise fish by slowly adding water from your tank into the bag or bucket they are in over a period of time so there is a slow adjustment to not only the temperature, but the water conditions.