Product review (5 stars): Buy this...don't waste time with anything else. Must have if you use a humidifier
This stuff actually works. I was having trouble with constantly having to clean my Vicks cool mist humidifier...it would get scummy and the wicking filter would turn brownish and crusty. I used the drop in tank cleaning cartridges that were recommended by the manufacturer and they worked for maybe two weeks (the month of sanitizing action that was claimed was stretching it IMHO)...that's just not good enough for me considering their price. I run my humidifiers CONSTANTLY in the winter and I was getting tired of replacing wicking filters and having to totally clean out the tray under the tank on a weekly basis - I'm a busy girl on a budget.
Read the reviews for this product and decided to give it a try. It really works. I add 5ml to the tank each time I fill it up (once a day) and I see NO MORE SCUM/BIOFILMS forming in any part of the tray, on the filter, or in the tank. No discoloration. I wish I had a before picture but attached is how my wicking filter looks after AT LEAST a month of constant use...clean and moist. Before using this product after the same amount of time I would see discoloration always in the filter.
Also I was pleased to see the large size of the bottle. I always expect to receive bottles of product that are much smaller than I had expected. This will last a long time - easily one winter and then some. I keep it right under the sink where I fill the tank along with a 5ml syringe ( I work in a lab). Easy peasy. Don't waste time with anything else.
 ps. I don't write reviews..so this product really impressed me