If the media was use more than one year it's better to get new one. if less you can wash it with distil water and run the reactor again . this way it will take few days till the media will start to react... with new one it will take little bit more time... .
if you need to buy media try to get the H&S media or the Schuran media the grain are big and better than the small one also it will not melt quick and not clog the flow
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