I'm sure this is all listed someplace, but can someone list all in one place the best levels of the following for Oscars?

Nitrate
Nitrite
Hardness
Akalinity
pH

Thanks!

nitrate...0 nitrite....0 AMONIA....0 ph.....6.0-7.2 the others you listed i dont test for these are the important ones...

I figured that was probably right on the nitrate, nitrite, & ammonia...thanks for the pH levels!

ammonia 0 at all times
nitrite 0 at all times
nitrates no higher than 40 just before your water change
ph can go from 6 to as high as 8. as long as the ph level is stable on the tank it wont adversly affect your oscars

if i may add, 6 to 8 pH is okey...but sudden change or fluctuation
sometimes do stress the fishes too. still you have to watch out for
erratic level.

its impossible to have 0 nitrate

i can assure you its not... my tank runs for a big part of the time with nitrates at 0....they only rize to about 5 just before a water change....if you keep them down they stay down