Product review (5 stars): Holmes liquid humidifier bacteriostat
So far, I haven't encountered any problems with this product and it does a great job at preventing mold and mildew and is working as stated.  I would recommend that you fill your water tank first, then put in the liquid bacteriostat.  If you use it first, it makes a lot of bubbles from the force of the water filling the tank.  I think it's a great product.