Tanks are heavy I'd actually suggest not moving in but cleaning it in place. With that in mind I;d also not suggest using bleach. Bleach must be washed off and very little residue left. That is hard to manage when you can't empty and fill the tank.

I use a scoop to remove loose substrate. A vacuum to get the rest of the substrate. I then use a steamer to start to kill bacteria, after a few steam cycles I'll wipe out the little bit of water. And use a chemical disinfectant (Chlorohexidine) REMEMBER it needs time to work (so does bleach for that matter) 20 min usually is a good rule of thumb. A steam hit follows and wipe down and 'mop' up of the liquid. than new substrate. And Yes I am terribly OCD.