Product review (3 stars): Seems to work, but foams a lot
This product is supposed to reduce or prevent growth of mold, bacteria, etc in the humidifier.  It seems to do that effectively.  However, if you add it to the reservoir first, then add water, so that it mixes fully, it foams badly.  The only way to prevent excessive foaming is to add the product last, then cap the reservoir and shake to mix.