This is a detailed description of what I did changing out my work tank. Smaller scale, of course, but maybe something will be useful to you. This is from a post I wrote a few weeks ago. HTH:
"I killed the power on all the appliances, and then began scooping the water into a styrofoam fish box (one of those they ship the fish in). I moved the rock and shrooms into the box and finished removing the top two-thirds into it, so the rocks were covered. I caught the ocellaris and dottyback easily with a bag (I never net my fish), and moved them to a specimen container, and covered it. I put that under a desk in the dark to minimize stress. I caught the serpent, and he went into, well, a 20 ounce coffee cup with a lid. Lastly, I removed the hermits.
Next I set the new tank in place, with a new inch of Southdown in the bottom, and removed the remaining water and existing sand to the new. As I began to get the tank filled, I started moving pieces of rock back. This was the hardest part, as I couldn't see through the 'milk' at this point (you all know Southdown!!!). I got the heater, skimmer and power head into position, and fired them up.
After the dust cloud had cleared just a bit, the animals went back in. Of course my clown has been swimming around the front all night since returning, but the dotty is still in hiding. I suspect I'll see him on Monday morning."
Good luck with the transfer!!!
