Reef safe DIY materials?

[sarinaruu]

i have a fair amount of hermit crabs and leaving shells scattered around looks so distracting, so i was thinking i want to do a small area with all of them in one place

what kind of materials could i use? i think i’d like to do some kind of square container and a “Free Shells” sign on top. any ideas welcome!

 

[exnisstech]

Small Tupper ware type container? I have a little one about the size of a can of sardines that sounds like it would fit the bill. No sign tho