You could probably re-use the sand, but I would recommend washing it. You could probably leave a couple of cups of the old sand unwashed and use it to "seed" the washed sand. Once you start pulling the old sand out of the 100 gallon system and see how dirty it probably is, you will see why you want to wash it.
You will go through a cycle on the new system regardless if you wash out the sand or not.
|