crabs new 24" cube

[i have crabs]

i thought the tank in picies was all made from foam and isnt even real rock,
i wanna cut a piece of regular live rock in half and see how solid the inside is compared to the reef rock if its solid with lots of holes i think it will hold well but if its crumbly like some of the less dense rock is then i think the rock its self might break apart while the silicone holds,
i think ill silicone all 3 back onto the glass and stick it in a bucket of water for a few days or a week maybe and we'll see how that goes i guess, im just getting ancy about getting water in the tank and its hard to hold out even though i know i should, maybe albert wont ship my pump in a timely manner and ill be forced to take my time