Ant Trap - for smallish hummingbird feeders

We have a over abundance of sugar ants where I live.
These are the most persistent little buggers ever!
Once they find sweetness anywhere they monitor it forever.
One of those things are hummingbird feeders.
Somehow, 1,000's of these little monsters found their way -inside- to the nectar.
I really don't want to give up hummingbird watching just because of the ants.

Today I am trying the attached file. It has a 3mm deep moat about 14mm wide.
Suggestions to date have pointed to vegetable