Turkistan Roaches

I'm planning on breeding Turkistan Roaches as a food supply for my alligator lizard colony, and eventual Leopard Gecko colony (don't have any yet, might aquire some leos next season).

I've got a standard 20 Gallon tank, which hopefully is big enough to breed them in sufficient quantity. Plan is to raise them on dry cat food, and use a smaller aquarium for gutloading before feeding to the herps. I've been told they can be gutloaded using standard cricket gutload.

Anywho, I have a temp question. Allegedly they need to be above 90 to breed. Is that measured at the base of the enclosure, or air temperature? I have a feeling I may need to put some kind of insulation on the glass (probably packing foam) to maintain the heat if it is air temperature.

Also, I've seen some kind of "water gel" described as the best way to keep them hydrated, but I have no clue what they are talking about - what exactly is this water gel thing? Are they talking about the same thing sometimes mixed with potting soil and used for non succulant plants?