I have been thinking of what I am going to do differently in my 125 when I add another one in my office and connect the two of them together via a 55G sump. I planned on soaking, scrubbing and cleaning then probably a quick power washing the two older crates, just like yours that I have been saving for this. Also, was considering saoking for a week or so before the change over.
My thinking was this way I am creating hiding places, making my current rock go farther and not increasing weight...
Let me know how it works...!!