I have suggested in the past that an excellent product to  use  as hides and  caves is ABS drain pipe, available in various sizes and  easily cut to desired lengths.  Being black,  it's also less  visually obtrusive than white or grey PVC, but as 
	
	
			 Fishman Dave
 
		 
	Fishman Dave
 mentions, it apparently floats in many areas; all the ABS I've ever  bought  or scrounged  in Canada has  always sunk; I'm sure  the  gummint has some obscure "buoyancy laws" that the makers must obey...
 
If you use PVC, there  are apparently some spray paints that will adhere to it and are non-toxic once cured.  I think 
	
	
			 FINWIN
 
		 
	FINWIN
 has some info on this.  When I've used  PVC in the past, I've  found it helpful to spread a bit of clear  solvent cement over the outside of the pipe and then roll it in, or sprinkle it with, aquarium gravel; it blends in  very nicely and looks less artificial that way.  Be sure to let it cure thoroughly.
Whatever you use, after cutting it to length you should at least   use a sharp knife to de-bur the sharp jagged cut edge inside and out, or better yet a rasp or file to smooth it.
That's a gorgeous fish; do whatever it takes to make the tank  suit the fish, rather than hoping for the opposite.  
