I see that commercial hummer food can contain Sodium Benzoate as a preservative. I have read there could be issues with this.

But I was thinking; what about Citric Acid. It's a common home preservative used with fruit. It's found in nature, often in fruit. If used in small amounts, does not affect flavor.

Could a small pinch, like a 16th of a teaspoon in 16 oz. act as a mild preservative? I usually change my feeder often enough that I don't get mold, but occasionally I get busy; one day no mold, next morning some mold spots.

I feel bad that they do sometimes drink some with a little mold spot, but I also don't want to add anything that will harm them. I think it the Citric Acid may hold off mold a day or so longer.

Would a tiny pinch of Citric Acid hurt them? Will eating a bit of nectar that has a spot of mold hurt them more? Will the Citric Acid not do anything one way or the other?
Just wondering.