When I upgraded from my 75 to the 125 I had to move the 75 1st. I took out all the sand (only 1"-2" deep) from the 75 and put it in a rubbermaid bin with a powerhead and heater. It was loaded with worms and pods. It sat in there about 2 weeks before I was ready to put it in the 125. When I started scooping it out to put in the new tank, it stunk so bad it was unbearable. I ended up thoroughly washing the sand in freshwater and then put it in the tank. So much for keeping my "live sand" alive.