Algicide also works. Benzalkonium chloride. You can get it as a 60% solution as a pool chemical and that will last forever. I use like 0.005% iirc. I make a 1%

Algicide also works. Benzalkonium chloride. You can get it as a 60% solution as a pool chemical and that will last forever. I use like 0.005% iirc. I make a 1% stock and dose that in, but I haven't used a humidifier in a while (prolly should)