I think it depends on how old and how deep the sand is. If the tank has been set up less than a year and is 3" or less you could do it. However this is coming from a guy that used sand from the ocean, so YMMV. Also, my order of attack would be to use a 3rd vessel of some sort, like a rubbermaid 30gal and put the LR
, water, and fish into, with a bubbler. Then stir the sand in the remaining 40 gallons and clean it off.
I would assume you have a sump that could hold some extra SW
and you have new SW
mixed and ready. If not, my LFS
gives 5 gal
containers with deposit and SW