Mist them once in the morning and once at night with rodi water.It will take sometime before the mangrove start sprouting. But when they do, the mangrove a nice to look at. When the mangroves start to sprout, spray the mangrove leaves with water, not salter but fresh water one a week. This will hydrate the plant. I used RO/DI so not to get the bad stuff from tap water.
Any other suggestions.