Product review (3 stars): An unexpected blackening of wick filters
The blackened areas on my two photos show what's been happening to my wick filters since I started using this clear, combination product a few weeks ago. I'm using the max of 2 capfuls per gallon because I noticed earlier in the season that more Holmes Water Treatment did a better job with mineral buildup.  I haven't been able to find a Holmes liquid so I purchased this.  It was all I could get quickly when my Holmes supply finally ran out.

With the Holmes prodict I also added BestAir's Bacteriostatic&nbsp;<a data-hook="product-link-linked" class="a-link-normal" href="/BestAir-3BT-Original-BT-Humidifier-Bacteriostatic-Water-Treatment-32-oz/dp/B000CMHLMG/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">BestAir 3BT, Original BT Humidifier Bacteriostatic Water Treatment, 32 oz</a>&nbsp;to my Vornado evaporative humidifier's two tanks without a problem each time I filled them.  Plus, during the season I clean everything but the filters w/bleach and then a vinegar soak to remove mineral buildup afterwards.

The wick filters are slightly different though---each now has a metallic grille-like piece sandwiched between two layers.  If the heating season weren't ending I'd try a new set of filters although the brands I've tried this year are all coming through with that metallic piece.

I've written RPS Products about the blackening and I'll update here if and when I get an answer.