Lori, here is how I did just the same thing not too long ago and it worked wonderfully for me. In your case you can add your existing sand on top of the new if its basically the same brand and grain size etc.. If you only have 1 inch, the chances of you having something nasty built up is slim, but its best to only skim off the top 1/2 inch or so and discard the rest.
Here is the method I recently used to redo my 1 inch bed into a 6 in DSB.
Now, putting it in an established tank. This is the only way I have had success doing it, others may have different methods. Start as early in the day as possible... sunrise (not kidding)
First get yourself a nice holding tank (20 gal) with an airstone and heater. (Cheap and can become your new quarantine tank). Pull water out of your tank into that new tank and then transfer over your fish, inverts and any critters you can get with a few pieces of LR for cover.
Next remove all your live rock and place into a garbage can, then drain water to cover that up with a heater.
Next drain your water as far down as you can saving it in another garbage can if needed.... do not stir up your old sand if possible.
Next scoop out all the sand and discard into a pile out in the garage someplace covered (youll be going back to it later and need a place where you can spread it around).
Rinse off the sides of the tank and get the bottom as clean as possible, draining it out again as best as you can.
Next... put in your new sand bed. As you pour it in,sift around with your hand taking out any rocks, shells or large pieces of trash that are in there.
Next... place a lid from a bucket on top of the sand and lay the end of the water feed line (from your water holding can) on top of that nad let the water hit it first. Let it run for a few minutes until the sand is just a littel covered. Use a low powered pump like a mag 5 at most, you want the water to fill in as slowly as possible.
Next run your hand through the bed again, adjusting the height and making sure there are no dry spots.
Next put the lid back on top of the sand and start filling again.... keep an eye on it and do no let any direct water flow onto the sand (youll get a really bad storm). Fill up about 4 inchs more then stop.
Next replace your rockwork and get it seated and solid and in the positions you want it. (You can also do this once your sand is wet). You may also consider a rock lift kit that will keep your rock off the SB itself.. Contact Bill at
bp@bendbroadband.com to get some photos of the lift kit. Its basically acrylic matrix with 3/4 rods with sharp ends to hold your rock in place. It sits on the bottom of the tank and you put the sand around it. This keeps the rock off your DSB improving DSB performance and eliminating the dead rock zones you get with burying rock and any undermining or potential shifts if you get burrowing shrimp etc. Its a neat product and a good investment.
Start refilling again until the tank is full.
Now that that is done, go to the pile of old say with a pair of tongs and a bowl of saltwater. Dig around in the sand and pull out as many of those lovely worms and critters that you can find from the old bed, into the bowel. Once you have done that, drop them into the new tank.... along with about a cup or two of the old sand.
Turn on the lights but not the pumps yet.. just the lights up top. Keep it like that until around 6 pm or so then turn the pumps on. This will give things the best chance to settle... you can then turn on the heater and get your tank up to temp, then transfer your critters from the holding tank into the new one.
You will always ahve some foam or residue on the glass or water edges, but it will go away in a few days. Just avoid powerheads for a week and only use the pumps for circulation, just keep the airstone in there to make sure the water is oxygenated.
