No, he's talking about the crystals used to hold water in miracle grow and other soils. They like to call them moisture crystals. You can use them. IT's been done. IT's just like using perlite or a vermiculite/mix. They are silicone based I believe. I might be wrong about that though. You could use them but you would have easier and a less expensive time by using perlite or the mix. You can look for the HEMPY Buckets to help you...
right here...

Derailed - Hempy bucket stylee - UKCultivator