I just move my dsb from a 20 and a 55 into a 135 about a week and a half ago. If there is hydrogen sulfide you are going to smell it an it's that really bad rotten egg smell. After skimming off the top inch or 2 of live sand and setting it aside, I expected stinky sand from the 55 and didn't get it. I did get it from the sand in the 20 so I didn't use the bottom portion of that sand, thought it was safer to get rid of it. I had my 135 full of saltwater that had been sitting for about a week with powerheads. I had a big rubbermaid tub, half a dozen instant ocean buckets and a bunch of baggies. We took all the lr out, put it in the tub with a powerhead and saltwater from the new tank, then baggied all the livestock seperately and foated them in the new tank. Then we took more water out of the new tank and siphoned in the water from the 55. Put all the sand back in, live sand on top, made a cloudy mess, put the live rock back in, then the livestock. Once we started we were finished within 2 hours. We have not had a spike and didn't lose anything. I think that is because we did everything really fast and acclimated our livestock like it was new. Also, we didn't use any questionable sand. Since it wouldn't make a 5 inch dsb in the 135 we have it going from 3 - 5 inches in places and will slowly add more live sand. HTH