The sand I use is CaribeaSea Aquarium Sand (color=black
). It is easy to clean and it sinks well. Even with the black color I don't have any trouble with dyes leeching out into the water. However, you will notice that sand that is on sale for $22 is clearly expensive. BUying my sand wasn't the most frugal choice I've made in my life, but I don't regret it. :)
My two 5 gallon long tanks have the footprint of 10 gallon tanks and I needed 1 bag for both tanks to have enough sand for live plants to root. So you should be good with 1 bag for 20 gallons. Unless it is a 20 gallon long tank with the footprint of a 29 gallon tank (like the tank I will one day set up). Then you would need two bags.
I will also mention that my sand isn't the only aquarium sand on the planet. It just happens to be the only sand on the planet I can give price, cleaniness, and needed amount estimates based on experience. But you will never find aquarium sand that is cheap for a larger amount like pool filter sand. T_T
I've never used PFS, so I can't make a comparison. Maybe someone else will be able to give you the other side of the story. :)