so i just got my first mantis today...he's a N. wennerae. He made a den that is kinda between some rocks and it is kinda open. i have some l/r rubble in the tank for him to build his home how he wants. how long will it take him to use the rubble to fix up his home??? also on Dr. Roys list of stomatopods it says that N. wennerae close up at night.....how will he close up an "open" den????