Recommendations for an amphibious SW crab

[Partially Submerged]

I am planning a 56 gallon tank with a raised plateau for mangroves. The plateau is about 8 inches high, and the idea is to keep it as a land portion until the mangroves have reached a certain height, at which point, I'll gradually raise the water level and the plateau will be underwater as well. Basically start with a paludarium that eventually turns into an aquarium. For the paludarium stage, I'd love to keep some amphibious crabs. Only challenge is, I need the tank to be full SW of at least 1.020 (i.e. not brackish).

 

Questions: 

 

1. Can fiddler crabs (Uca sp.) thrive in saltwater? Preliminary googling suggest they can, but since they are usually found in brackish water, I thought I'd ask?

 

2. Are there any other species you can recommend? I'd be nice if the crabs spent at least part of their time in the water. 

[BlennyBoi]

id go the fiddlers. you could also get some mudskippers. both need a good amount of mud to burrow in tho