I've noticed it mentioned a couple of
times on this forum that if you have a sand nest you won't be able to
see the ants. The reason for this is that they will
tunnel away from the light.
My current farm is Ytong. I cover it with black card and have a heat lamp shining on this card for a few hours every day. When the lamp is on the ants move right up to the glass. They go as far as to attach eggs and larvae to the ceiling for the extra heat. When the lamp is off, they go to the part of the nest which retains it heat for longest, usually a plastic tube.
I imagine that if you try the same thing with a sand nest, the ants will dig right up to the glass to get to the heat. I'm thinking of trying this if I catch any queens this year.
Has anyone else tried this?