Would This Work As A Cave?

[taffia1]

I'm trying to get ideas for an aquascape which will house a red tail black shark.  I've got some redmoor root soaking but I want to incorporate more caves, nooks and crannies.  I don't want any artificial caves so I was thinking of the following idea, would it work?
 
On one side of my tank build up a mound of substrate (ada) with a back PVC pipe buried in the middle, the pvc pipe would have holes drilled in the bottom so any (or most) fish waste would drop into the substrate.  The mount would be planted concealing the entrance and also use up the fish waste which drops through the pipe.
 
Would this work or would I just be creating an amonnia environment within the cave?
 
Any other ideas are most welcome for a natural looking/hidden cave.
 
PS I'm going for a triangle aquascape so the mound would level out into a flat surface where i'de create a lawn effect either through HC or dwarf hairgrass
 
Thanks

 

[liamsmith15]

I've found 9 times out of 10 that the RTS ignores whatever you make/buy for them and just picks, what I would consider as the worst place eve. But hey! I'm not a fish!

 

[falcon1]

My rainbow prefered a cave I made from two small rocks, with a large flat one on top. He didn't really spend much time there anyways. Spent most of his time patrolling the tank. Like liamsmith, he rarely used the amazing and spacious cave that I provided.