The birds are not using the feeders because they are on your deck which is Too close to people. Also, do you have cats or dogs? The birds see them from the deck and are afraid to approach the feeder. For the same reason, don't put the feeder in front of the house. It is not isolated enough for the birds to feel comfortable.
I think the best place is several feet away from the back deck. If you have no trees, get a freestanding pole on which you can hang feeders. I have seen them at F&S.
I have trees so I have suet, bird feeders, and a waterer hanging on them. I also have a tree stump on which I have a large seed feeder, which is used by a lot of birds. I think you can put a feeder on an old table, too. Just remember to put the seed at least 2O ft. from the back deck.
As for the ants, I don't know...we don't get ants here. However, please don't use any poisons for the birds', wildlife, and pets' sake! Good luck.