You can use any synthetic aquarium micron filter pad that is sold in large enough pieces to cover your needs. Coralife, Dr. Foster and Smith and others makes them. The idea is to have a second layer on top of screen that will prevent the smaller substrate particles to fall through into the false bottom area.
Thanks You Carlos! I appreciate the response.
Heat pads used in frog tanks are highly inefficient since heat will escape to the air around them. Members do use them in combination with the light bulbs when a species require a warmer environment. For species requiring high 70s or low 80s you would look at other options like heat tape as well. Recommend first decide the species you plan to keep, they might not need supplemental heating at all

.