Goby and Pistol Shrimp move decison (?)

I have for a year been watching the relationship the goby and pistol shrim have in my refugium. I have sand in theeir home now, and the pistol shrimp is constantly making new homes. They have about 6 different ins and outs in their burrow, but they collapse easily. Lets say the pistol shrimp earns its keep. I recently started 151 gallons of a 3 step waterfall system that extracts water from my main 120G reef sump and returns. The tank is running and running good. I have decided that the 1st tank will be fishes that are not reef safe and that is desirable since I miss being able to have those fish. The second smaller tank I would like reef safe, and then lastly the smallest perhaps some clams. I am wondering if the crushed coral, about 20 times the size of the refugium grain would be too heavy for the pistol shrimp. I imagine in comparison to his own weight, his lifting abilities are incredible. I just didn't want to put him in his larger home if he would be crushed. Another is, if I choose so, in the 1st tank, will lemonpeel pygme angels or any of the smaller dwarfs eat him. So basically is the bigger cube 27x 27x 27" that is not reef safe good for them? Or should the 2nd reef safe one be better, or is the gravel going to be worse than the sand. Will I still see the activity. Divided among the first 2 tanks I have 250 lbs of florida baserock. Its nice in the refugium because they are always noticable, but unfortunately when I feed Rod's Reef the goby is picky choosing select peices and letting the other pieces rot away. Nitrates are low, but I would like to do what is best. Assuming that I put them in first I have no doubt that they will find eachother, but will they be safe in all regards? Any comments please are helpful.

Picts

The dwarfs shouldnt eat him

But you should not get crushed coral because it will damage your gobies gills. Also if you are having nitrate problems with sand, crushed coral will make them worse. The crushed coral just traps the uneaten food, fish poop and other detritus, letting it rot and release nitrates back into the water column.

+1 little fish

That is a really neat set up you have is that a store you own or is it just a massive fish room. Either way I am jelous. I have about a 2in tiger pistol and its pretty amazing at the weight he lifts. He will pick up turbo snails (thinking that they are empty shells) to mark entrances to his burrow, and other large pieces of rock realative to his size, so I think you would be fine. I do however agree with little_fish and smitty that sand would be a better choice for Nitrate reduction. I would also put the goby and pistol in the reef section of the tank.