If we don't reach the minimum buy of 40 boxes of Reef Crystals as we approach the 15th of March, you can change your order. Sub out - no, but you can change your order. We will only order what you request/pay for. As we approach the minimum 40 boxes of Reef Crystals I will post the status (currently 13 boxes). I'll try to find a deal for Reef Crystals. Chewy has the bucket, not a box, for about $38.