Did you look at this page:http://www.poolsolutions.com/gd/kiddie-pool-care.html or the Super Simple Recipie page on PoolSolutions.com? The kiddie pool page is fine for 480 gallon pools.

I seriously doubt the pump uses 1800 Watts - something's wrong with this number.

I'd suggest you follow the kiddie pool plan referenced above. Dump and refill the pool monthly and when there's a fecal accident and when the water gets cloudy or a hint of green. Run the pump whenever no one's in the pool.

Let us know how you plan to proceed and how the water looks.