Son bought a used tank with existing substrate

[baldislife]

Hello

My son bought a used 45 gallon JBJ that had been established for a over a year I believe. It was a great Offerup deal he couldn't resist. He kept the sand wet and has the existing media. Should he keep the sand and media and refill to keep the bacteria already built up?

 

[MnFish1]

I would rinse it extensively. And then use it. The problem is that anaerobic sand (without oxygen) - is not helpful - and may be harmful