Re: Cockroaches in Vivarium - Is this plan OK?
I wouldn't count on feeding off days in juxtaposition to reach gel in your viv.
Using behaviors that are predictibly consistent to manipulate by combining harmless attractants means no assuming or wishful thinking.
For anyone worried about applying a small UTH against the side of a viv, you are worrying needlessly as the mats themselves are predictable and easily measured. A small one will produce a warm spot on the glass with a rapidly vanquishing outward drop within an inch or two interior especially if no insulate material, hobby board, polystyrene flat, etc, is used to back the glass the pad is attached to.
No poison required. No risk, unless you are taping the frogs to the warm spot on the wall.