Try one of these, someone just suggested them and they are the perfect fit: HoMedics Ultrasonic Demineralization Humidifier Replacement Cartridges | 4-pack | Prevents Hard Water Build-Up | Filters Mineral Deposits | Purifies Water | Eliminates White Dust | Removes Odor https://www.amazon.com/dp/B00EW1QLW4/ref=cm_sw_r_cp_api_glt_fabc_RG7QVB9M9PTHCRPZWEPJ?_encoding=UTF8&psc=1
I use these in a one-gallon ultrasonic humidifier. One of these lasts most of one grow.
.
These came w my Homedics humidifier:
Ultrasonic Demineralization Humidifier Replacement Cartridges | Prevents Hard Water Build-Up | Filters Mineral Deposits | Purifies Water | Eliminates White Dust | Removes Odor | HoMedics - 4 Pack https://www.amazon.com/dp/B00EW1QLW4/ref=cm_sw_r_cp_api_glc_fabc_f459FbAX1Y8F7
I have multiple taotronic brand humidifiers. Tap water with a demineralization tab in there
HoMedics Demineralization Cartridge for Ultrasonic Humidifiers | 4-pack Replacement Cartridges | Prevents Hard Water Build-Up | Filters Mineral Deposits | Purifies Water | Eliminates White Dust | Removes Odor https://www.amazon.com/dp/B00EW1QLW4/ref=cm_sw_r_apan_glt_fabc_6RPAGW96VT2GDCZW60CV?_encoding=UTF8&psc=1
Someone else turned me on to these bad boys: HoMedics Ultrasonic Demineralization Humidifier Replacement Cartridges | 4-pack | Prevents Hard Water Build-Up | Filters Mineral Deposits | Purifies Water | Eliminates White Dust | Removes Odor https://www.amazon.com/dp/B00EW1QLW4/ref=cm_sw_r_cp_api_glt_fabc_W5NYG7B50D1DMFWW7PBA?_encoding=UTF8&psc=1
I was just suggested these too: HoMedics Ultrasonic Demineralization Humidifier Replacement Cartridges | 4-pack | Prevents Hard Water Build-Up | Filters Mineral Deposits | Purifies Water | Eliminates White Dust | Removes Odor https://www.amazon.com/dp/B00EW1QLW4/ref=cm_sw_r_cp_api_glt_fabc_RG7QVB9M9PTHCRPZWEPJ?_encoding=UTF8&psc=1
Every humidifier I've ever had has build up like that. I use these in order to prevent it. Give it a good scrubbing to remove what you have. Use a brush, sponge, etc. It'll be annoying because of the nooks and crannies in the machine, but once you're done, plop one of those in the tank and it'll be good for a month or so.
I have a homedics total comfort. Your other option is to buy one of these for any humidifier
Homedics UHE-HDC4 Ultrasonic Humidifier Demineralization Cartridges https://www.amazon.ca/dp/B00EW1QLW4/ref=cm_sw_r_cp_api_i_txDfCbAXV3HKJ