I just bought this quikrete playsand for my new substrate. I have an 30 gallon established freshwater aquarium with gravel and 10 fish in it with an amazon sword and an anubia. Can you give me steps on how to change my substrate. I was thinking on changing half the gravel to sand and a couple days or a week later I change the other half. Is this a good idea? Any tips would be much appreciated. Thanks for your assistance upon advance.