Ideal Mix for Container Grown Navel Oranges in Zone 8

Hello,

I live in the PNW and am trying to grow some citrus. For info, our winters mostly hover around 5-8 degrees Celsius at coldest (with exceptions of course) and don’t get snow every year, and when it does it’s for 1-3 days and then it’s gone and doesn’t come back. In the summers we’re usually around 24-30 degrees Celsius.

I recently bought a 2 year old navel orange tree and have been playing around with different mixes of soil. I realize I need to be aiming for good drainage so perlite has been used in all my mixes, but I saw someone recommend blending in about 1/3 vermiculite, so I’ve gone 1/3 of each vermiculite, perlite, and Original Sea Soil (enriched with fish nutrients which I hear is great!). I heeded the advice with vermiculite solely because this guy mentioned it’s inorganic which means it won’t break down, and will create a nice airy environment for my orange. Is this the right choice, should I be aiming for something else?