There are seed eating ants, but generally they eat the seeds that are on plants (when the plant has grown and matured and set seeds). I have never seen ants bother any of the seeds I planted (I can't say that never happens, only that I haven't seen it). Most often ants are pretty harmless in the garden.
If you do want to get rid of them try typing ant control into the Search the Forum feature. You will find a bunch of stuff written here already about it.
Here's one thread to start you off: