The general idea is about 1" soil and 1" cap. You need to make sure you have good flow to avoid dead spots.
If you don't let your filter dry out and safe water is used then you shouldn't lose the BB in your filter. Having said that, I still feel that the soil will leech ammonia into your system, especially if you don't have a lot of plants to absorb it for you. I would stock with caution and test your water.
If you don't let your filter dry out and safe water is used then you shouldn't lose the BB in your filter. Having said that, I still feel that the soil will leech ammonia into your system, especially if you don't have a lot of plants to absorb it for you. I would stock with caution and test your water.