Just 3 weeks and I am already experiencing some algae growth in the humidifier drip pan. And that's with using distilled water! I guess it's really no surprise since the outside temp has been over 100 each day for a month now. The inside temp gets up to around 77-80 max but still kind of warm. It's a perfect incubator for mold and algae growth. I found this first little colony early on when I was making the float valve connection to the unit. I simply removed the pan and washed it. My intentions are to control the algae with a Dimethylbenzyl ammonium chloride compound in tablet form. This would provide a biodegradeable, non-corrosive and non-toxic treatment with no detectable odor. The solution does not evaporate into the air but adheres to the pan with somewhat residual protection. Most likely a dose of 1 tablet per week will keep things in check. Mold spores are another problem all together. The damp humidor environment would be a prime breeding ground for black toxic mold. I don't want to ever see toxic mold in the humidor so I will soon be installing an ultraviolet light source (UV-aire) similar to the sterilization lamps used in the medical field. UV in a large dose will kill just about anything. Mold spores passing within 18" of the lamp are zapped dead. The main disadvantage is bleeching. I will have to fan force the air through a metal chamber containing the lamp so as to continuously treat all the air within the humidor over time while shielding the UV light from the cigars. I'm already familiar with this arrangement as we have a larger unit already installed in the central air conditioning return air chamber. It's a bad dude. When first installed we could actually smell the plywood cooking, not from heat but just from the intense UV rays.
Just a little update on progress. Everything else is working as planned. RH is now controlled at 64-66%. Automatic water fill is working. After 2 weeks of storage the cigars are already stabilizing. I had several different brands that were busting wrappers when kept at 70%. Now at 65% they are burning perfect.