ph levels and oscars

Question
I have had my 75 gallon tank set up for about 2 months now.I checked my pH today and it was off the chart 7.5 or higher. I bought a pH decrease and added it today and also done a 40 water change will this solve my pH problems. I added the pH minus about 2 hours after water change checked it before and it was still off the chart.  HELP one more thing I have 4 Oscars in the tank and they fight each other bad how can I try to stop that if possible.

Answer
Shannon:  Oscars and most tropical fish will do just fine in a tank with a pH of 7.0-8.0.  Fish can tolerate changes in pH so long as they are not rapid changes.  Have you added anything to your tank that may have caused the increase?  please let the tank come back up to 7.5 and do not add anymore chemicals to the tank as the fish will do better with the higher pH then when the pH fluctuates a lot.  keep me posted... dave