Not sure if a 55g would be much harder than a 29g, but I did mine yesterday. I made the switch from cc to southdown sand I bought at Home Depot. 50lbs for $5.99. I did it last night. I put half of my water in a large rubbermaid garbage can, then the rocks and fish and inverts, and then the rest of the water. I removed the cc with my fish net and replaced it with the sand and slowly added the water back. I left a couple of handfuls of the ls that was already in there. I filled the tank (29g) up about half way with water, added the lr back and filled the rest of the way and finally added the fish and inverts. The process took about 4 hours. I ended up with a sand storm even though I was really careful. The sand has mostly settled but am told it will take about a week for it to completely settle. I also added Nitromax (a live bacteria) to help with the cycling.