feeders have a little mold growing inside them.

[JP]

I just filled my feeders up with sugar water, & noticed the feeders had a little mold growing on the inside of each. they are glass, quart jars. Should I have used clean jars? or, a little mold won't hurt. The feeders had about 1/5 sugar water left in them. thnx, JP.

[Horns Pure Honey]

It wont hurt them but I clean mine every once in a while, I just like all my stuff to be clean :D

[Rich V]

I would also get a little black mold. They say it will not harm the bees, but I always clean it out. Maybe I'm overly cautious because I'm new at this.

[Michael Bush]

I feed syrup even if it's moldy, but I like to let them clean up the syrup and then wash out the feeders with distilled vinegar to get the mold out.

Bees can actually filter all of that mold out.  They can even filter out the smallest particles of pollen from nectar.