Welcome to the forum from the UK however I think you have your sums wrong as your pond is quite sizable at 5ft x 4ft x 5ft and is more like 600 gallons not 60 gallons perhaps more.
Its a nice size pond but I'm not up on US fish so cant answer for you if its good enough to keep 4 rock bass .
What is your filtration like i;e is it man enough to do the job its there to do ( important to your fish ) if you wish to keep them they have to have a beefy sized flter for that sized pond, whast U.V-C are you going to use and what size airpump?.
These are all very imprtant questions you'll need to answer for the survival of any fish be it rock bass or anything get things wrong and your in trouble.
If you can meter the water into your pond to give you the right gallonage for your pond which will in future be needed for any treatments you'll need .....
Buy some Microbe_ Lift PL filterpad innoculent gel and follow the instructions on the bottle it should kick start your pond within a few days, we use it all the time its really good stuff .
rgrds
Dave