Bioactive substrate depth question

[Sunnysenorita]

I'm converting an armoire into a bioactive viv for my male ambilobe. I'm just about at the point of installing the substrate box and I'm wondering what the sweet spot is for depth? I'm aiming fo 9" deep in total, which after the false bottom/drainage layer leaves ~7" for the actual substrate. I've seen that 4" or 5" is sufficient, but it's a large enclosure and I need enough depth to plant decently large plants. Does this sound right to everyone? Will 7" be enough for a few larger plants? Is it possible to be too deep (in regards to biological balance, fauna etc)?

 

[jamest0o0]

All that matters is you have enough depth for plants. A bioactive substrate could be a half inch if you wanted. Take it from me, I've done everything from that to 2 feet deep. They all accomplish the same goal.