I too have occasional problems with ants, yet often they don’t find the feeder, it’s strange. I’ve had the feeder hanging on the clothesline, and the ants found it, yet right now I have a feeder sitting 18” from the handrail on the front deck with no formicae at all, even though the sugar ants just outside my garage swarmed yesterday.
I think it may have something to do with there being a small drip, and the ants go looking for the source once they find a sugary spot.
The first ant invasion were little black ones. The second invasion has been large red ants. I moved the feeder a little bit, maybe 2 feet, & that might have made a difference, who knows! The new moat looks a lot more “formidable” so we’ll see how it goes :-)