Refugium questions

[Lilxxwojo1]

Ok so I have heard conflicting things about the depth and type of sand/mud in refugiums... And now I am not sure how to proceed so here are my questions:
1. How many inches of mud/dirt should I have? I bought some mud and I have about 2 inches now but I have read that I need much more.

2. Do I have to use refugium mud or can I mix it with live sand or any other substrates? (the refugium mud is quite expensive)

Thanks for your help guys!

 

[mr_X]

Mud is not necessary and I have never heard nor seen any positive results from it.
You don't even need sand. I like using some though, maybe a couple inches just for the sand dwelling critters and more surface for bacteria.