I have around a dozen of what I think is Ligia oceanica and currently they are housed in a cage with tissue paper, shells and bark but I am switching them to gravel soon. I gave them turtle food to eat and should I do anything else?
Orin McMonigle has kept and bred Ligia exotica, he kept them on a substrate of sand drenched in artificial sea water, and he feeds them freshwater algae, dead leaves and seaweed, along with dog food, fruits and veggies, etc.
There should be shallow dishes filled with salt water for soaking, but make sure there are pieces of wood or a slanted rock in the bowl to allow them to climb back out.
He also says you should provide extra hides for the mancae or remove them, as the adults tend to trample them.
Hopefully this helps, don't know if these care parameters will work for L.oceanica, but it's worth a try.