That works if you're moving substrate yourself. But if used substrate has been closed up in a box for days, the N-bacteria have most definitely gone through a die-off. They're aerobic so need good water flow to ensure they're getting the O2 they need. Using this without cleaning it first could very easily be toxic. Even just moving substrate around too much can cause a die-off in a tank.i can certainly understand the need to "purge" the substrate of it's history by washing and drying it....but there is also a reason not to do that if you know the substrates history...you're buying a substrate that's already got it's good bacteria going, you don't have to cycle your tank....or don't have to cycle it as long. Lots of people like to start tanks with mulm and substrate from established tanks.