as i said i had a massive problem last year when i pulled my carrots up (and there was about 200) and all of them had no inside left just skin and about 30 red ants in each same with strawberries raddishes sweed and everything else that grew underground i really am stuck it being my first year i was really proud about how they all looked as the greenery above ground was not touched and looked wonderful i have to admit i had to cry at one stage i was so dissapointed. will ant powder be absorbed into the plant when it drinks the water i give it? i dont want to be poisoned!!
It certainly
wasn't the ants that ate your carrots, I promise you, although they were obviously around at the time
It sounds like a bad infestation of carrot fly. These flies lie their eggs at the base of the tuft of carrot leaves and their grubs eat tunnels into the carrot roots, leaving brown marks and empty bits.
This is easy to deal with and all you need to do is protect the seedlings from now onwards with fine netting -- I used old net curtians once over aframe made of wire coathangers opened out. Make sure you fasten it down well so they can't get in at the bottom, by heaping earth over the edges.
There are more fancy ways of dealing with the little blighters too. Some pepole put up a barrier about 2 ft high all around the carrot area as carrot flies only fly low. It is the small of the leaves that atttracts them, so very careful thinning and not leaving thinnings lying around will also help.
Hope that is helpful. Good luck