I have had no trouble with mold using these approx. 4.0-4.5 gal feeders
since I started adding 1/4 tsp cream of tartar/gal of syrup as suggested by
someone on this list. I refill about every 2 weeks when feeding. I
should attend to it about every 10 days less, as they are always bone dry
when I open up.
HBCanon
Geneva, FL