Rethinking refugium Substrate

I've have my 125gal setup for about 3 months now, and its fully cycled and i have a 55gal tank converted into a refugium under the tank. I read a post about using pure clay "kitty" litter which is totally safe, but the other member used another 4in of sand on top, which I have not... I am now rethinking that since the pure clay I have is medium size grains, not fine like sand which could trap things... did i screw up? is it to late to add sand?

 

I can't say that its too late, buy look at Packs thread & check out his fuge pics.....NICE!!!!!

 

I'm settin up a refugium as well and I have my bag ok litter ready to go but unsure if its necessary to put sand over it or if I'm ok just puttin the litter in and running it. I could see how stuff could easily get trapped in the litter it self due to its size so I guess it would probably be a good idea to put sand over it.

I don't see why you couldnt still just put sand over it.

 

the reason im hesitant is because since its already been in there a while i don't want to trap anything already on top of the kitty litter.