Product review (5 stars): It works well and I haven't had trouble with the water turning bad at all
<a data-hook="product-link-linked" class="a-link-normal" href="/BestAir-3BT-6-Original-BT-Humidifier-Bacteriostatic-Water-Treatment-32-oz/dp/B000CMHLMG/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">BestAir 3BT-6 Original BT Humidifier Bacteriostatic Water Treatment 32 oz.</a>
I use this product every time I fill the tanks on my humidifier.  It works well and I haven't had trouble with the water turning bad at all.