keep the tops extra moist with fresh water until the damage reverses if there is browning/damage to the stalk. Brittle pieces should be removed.
as to why the top might be dying - how is your magnesium? mangroves need mag to bring water to the top portion of the tree...try for 1200 or a little better.
QUOTE (hlander @ Feb 25 2010, 09:03 PM)

Can I grow a mangrove in a rubbermaid bucket and when it gets bigger transfer it?
you will want to keep it small with trimming and some people also pot the roots to encourage the roots to grow densely instead of out. If need be you can always trim the roots too, but you must be sparing when you do this. If you transfer a tree, (as opposed to a seed), it should be drip acclimated over a pretty long time, (6-10 hours if you can do it), to minimize stress. Acclimating them to new soil, (if that is an issue), should be done too. Just helps to minimize stress in the transport.