Sand Bed?

[OrionN]

A sand bed hold lots of nutrients in it. I would not reuse a sandbed. You may want to use some of it to seed an new sand bed. My experience is that once a sand bed full of worms and life was disturbed, it will take a long time if ever to become stable again. Of course how bad this is depends on how full of nutrient it is. Imported live sand from the reef do not really hold anywhere near as many animals as the sand typical of our tanks.

[OrionN]

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My concern is its not trying to save a couple of bucks on sand, its cheap relative to the new DSA 140 tank, but to have all the bacteria that in the old tank to the new.

I think your should try to minimize the amount of nutrients in a tank. The bacterial is unimportant. They will reproduce and multiply very quickly.
Many people who used to have a deep sand bed (I am in that group) recommend a remote sand bed (remote from your display tank) so that you can remove and exchange them for nutrient removal with minimal disturbance to the tank.

[Bill S]

As a molecular geneticist by education (and therefore a microbiologist), all it takes is a cup of old sand. Most bacteria double in less than an hour - some as quickly as 10 or 15 minutes.

Remember the old chessboard equation. Put a grain of sand on the first square, 2 on the second, 4 on the 3rd, 8 on the 4ths, etc. By the time you get to the 64th square, you have a pile of sand a mile high with a mile base.