ph level, your tap water is probably fine.
Temperature should be between 78-82 fahrenheit, I use 81 or 82 on all my tanks.
As for getting ready with the water, look up cycling and how to cycle your tank before adding your fish. It will take about a month but you really need to do this to have healthy fish. I'd consider three piranhas for that 55 gallon and you should be good to go.
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