I've been trying to keep mangroves for about a year and a half and have reached what I think is a somewhat successful batch. I've tried many from different sources and the best result was +50% success rate with the buy 50 pods on Amazon and root them yourself approach. (I could have gotten better, I was just lazy with getting all the pods floated.)
The key factors I feel were:
1) Be very careful with the roots and leaves. If you get a break, it's going to be a goner.
2) Lots of light
I misted them with RODI in the beginning and now, I leave the leaves alone and can pour any water on the stalks to clear the salt creep.
The roots get pretty unwieldy. I've yet to "plant them" but plan on having them in their own refuge section soon.
I would worry about the roots clogging up the overflow.
These I bought in March: