ProTec PC-2 Humidifier Tank Cleaning Cartridge, 2-Count Packages (1 pack of 2 cartridges)

Do not buy the generic ones! These have anti-bacterial component that definitely delays contamination of humidifer water which happens sooner or later. Make sure you replace them every month

Got these as I was finding goopy stuff in my humidifier water. These work perfectly - keeps the water (and the filter!) clean.

Tried other similar items and these last longer and control the junk that builds up in the humidifier better than any other brand. They are now the only brand I buy.

Have included one of these in the water container of a new humidifier every day for a couple of weeks. No sign of slime or discoloration in the well or inside the container itself. I do rinse the container and put in fresh water every day. We'll see how long it's able to do a good job.

I recently moved and do not have my whole house water purification system. The water in my tank was causing mold/ fungus to grow on the filters within a week. It didn’t help using the filtered water from the refrigerator. I found this product and no more growth- my filters are lasting longer. Has a black substance the first couple of days and then it clears up.

These things are awesome! We are on well water and our humidifier would relatively quickly build up a slimy, brown film all along the entire inside of the tank and the diffuser housing. We thoroughly cleaned the humidifier and dropped one of these in and never get any more slime! Totally cured the problem. I never liked not knowing whether that brown slime was getting atomized and into our lungs. Now I don’t have to worry about it at all. We bought a two pack and the first one lasted for well over a month before I finally decided to change it because the crystals inside were slowly dissolving and leaving a very fine powder on the bottom of the humidifier. I wasn’t worried about that powder getting picked up by the diffuser, but thought perhaps it might clog something up over time if I let it collect for too long. I will definitely continue to buy these!

Dropped one in the water tank and we had no white dust in the house. Changed it every 30 days. Used sink water.

They don't really work to eliminate the white dust from hard water. To be honest, I'm thinking now that that's not what they are meant to do. I can't tell yet if they help keep the humidifier cleaner inside or not.