Re-do

[steelwrap]

I've got a 55 FOWLR thats been up about 5 or 6 years. I'm wanting to go a different route with it so this weekend I'm going to pull the live rock, get rid of current fish, give walls a good cleaning, remove/clean top layer(1/2" or so) of sand bed(about 3"-3 1/2" deep) then reaquascape. My questions are:
1. Do I need to keep rock submergered or just wet?
2. How big of a die off/recycle should I expect?
3. What are my chances of releasing some nastiness into My tank with messing with the top layer of sand?
4. Would a dose of chemiclean be a good idea? Thanks , Jeff

[steelwrap]

5. Would dosing with vinegar be a good way to boost My bacteria back?

[fishgate]

If you are going a new way, I'd just redo the entire thing. Put your rock in a dark tub of SW with a powerhead. I'd probably just toss the substrate but if it is still decent, rinse it thoroughly and put it back in.

You will get some die-off since you have removed the source of food for your rock. But you should have a shorter cycle by adding the original rock back in. Your bacteria will increase to the level required for the available food in your tank. Once stabilized, add a few things at a time to allow the bacteria to expand as needed.