Welcome to HCA! Good for you, for rescuing a crab! That's awesome that you've been doing your research and care so much about her!!! You're in good company here at HCA!
I assume you've seen them, but they're just so awesome - link to HCA care sheets is here:
http://www.hermitcrabassociation.com/ph ... m.php?f=51
One thought, if she's an E, minimum recommended substrate depth is 10-12", especially once she has a buddy, to prevent Ecuadorians from digging up molters. Also feed plenty of protein. The safe food list has many options.
In your search for more crabs/species buddy for Sapphire, have you checked out the HCA adoption forum yet? There may be some crabbers in your area wanting to re-home crabs, or some folks on Craigslist wanting to get rid of their crabs. Adopting crabs from previous owners is a good way to avoid supporting the pet industry (all land hermit crabs are wild caught and transported in horrible conditions), and often the crabs will be less likely to die from post-purchase syndrome (PPS) once you bring them home. There may not be anyone in your area trying to re-home their crabs, but I figured it couldn't hurt to look.
Have you seen the pics/video of crabs on the hamster wheel yet? If you're getting a 20 gallon tank, you might have space for one. Personally, I think it's the funniest thing ever, watching them walk on a hamster wheel.
If you haven't already purchased it yet, please be advised that getting the largest tank you can is probably a wise use of resources. Many crabs double in size in a year, and can live 10-20+ years in captivity given optimal conditions, and it sounds like you plan to give your crabs the best crabitat ever! Once they're jumbos, recommended tank size is 100 gallons (to give them the tank width to walk around well), and they need at least 15+ gallons of space each. More details in the HCA care sheets on sizing your tank for the size and number of crabs you have or plan to have.
EDIT: Second-hand tanks work great for crabbing. It doesn't have to hold water. Craigslist, Bookoo, Letgo, Offerup, consignment sales and thrift stores are good places to look. And occasionally Petco and Petsmart have 1$/gallon sales for tanks 40-50 gallons and under if you're in the USA.
If you have any questions, please do let us know. We're here to help!
Happy crabbing!!!
