You DEFINITELY don't have enough rock. It's not opinion. Live rock is a natural filter. Your bacteria colony which resides on surfaces is limited with the tiny bit of rock, substrate, and glass. Also, you don't have enough rock to process nitrate. I don't care what the hobby grade test kits say, but eventually, you will see the by products of not enough rock. Unless of course you do water changes like a mad man. If you plan on keeping a very low bio load, then it's not a concern, but I doubt this is the case.
we use rock because of the anaerobic zones in it that house bacteria to process nitrate to nitrogen gas which is removed from the tank at the surface. Your tank is missing this component.
I have seen all sorts of fish do all sorts of things. I'm just pointing out something I am noticing. Also, the fact that foxface are omnivorous and like to graze, I personally, would like to have a substantial amount of rock for it to graze on.