[Raul-7]

For a newbie, Eco-Complete is the way to go. You should add some peat to the bottom though..

 

[Raul-7]

Substrastes will always mix together...small particles tend to move the bottom, larger at the top; so don't worry about mixing..it's a natural thing. Peat is great, it has a high CEC(ability to store and transfer nutrients) and it creates an acidic environment. Unfortunately, PowerSand isn't available in the US, but it's basically a mixture of pumice and peat.