pool filter vs. play sand

[MHcblues119]

Im starting to test things out in my 55g so when i get my big tank ill know exactly what im doing.
Which sand is better for tank use?
And is it a bad idea to switch my gravel out and put sand in while i have fish in the tank?

 

[Jkessler623]

i have a 55 with pool filter sand.looks great.just be sure to rinse it VERY well.once you rinse it only the bigger particles will remain and it wont cloud your water and it looks great and its easy to clean